AAT 10-Q Quarter ended March 31, 2012

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-Q

For the quarterly period ended March 31, 2012

or

For the transition period from to

Commission file number: 001-35030

AMERICAN ASSETS TRUST, INC.

(Exact Name of Registrant as Specified in its Charter)

(858) 350-2600

(Registrant’s Telephone Number, Including Area Code)

Indicate by check mark whether the Registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. x Yes ¨ No

Indicate by check mark whether the Registrant has submitted electronically and posted on its corporate Website, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the Registrant was required to submit and post such files). x Yes ¨ No

Indicate by check mark whether the Registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer or a smaller reporting company. See definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check one):

Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). ¨ Yes x No

The number of Registrant’s common shares outstanding on May 4, 2012 was 39,286,206.

AMERICAN ASSETS TRUST, INC.

QUARTERLY REPORT ON FORM 10-Q

FOR THE QUARTER ENDED MARCH 31, 2012

2

American Assets Trust, Inc.

(In Thousands, Except Share Data)

The accompanying notes are an integral part of these consolidated financial statements.

3

American Assets Trust, Inc.

(Unaudited)

(In Thousands, Except Shares and Per Share Data)

The accompanying notes are an integral part of these consolidated financial statements.

4

American Assets Trust, Inc.

Consolidated Statement of Equity

(Unaudited)

(In Thousands, Except Share Data)

The accompanying notes are an integral part of these consolidated financial statements.

5

American Assets Trust, Inc.

(Unaudited)

(In Thousands)

The accompanying notes are an integral part of these consolidated financial statements.

6

American Assets Trust, Inc.

Notes to Consolidated Financial Statements

March 31, 2012

(Unaudited)

Business and Organization

American Assets Trust, Inc. (which may be referred to in these financial statements as the “Company,” “we,” “us,” or “our”) is a Maryland corporation formed on July 16, 2010 that did not have any operating activity until the consummation of our initial public offering (the “Offering”) and the related acquisition of certain assets of our Predecessor (as defined below) on January 19, 2011. The Company is the sole general partner of American Assets Trust, L.P., a Maryland limited partnership formed on July 16, 2010 (the “Operating Partnership”). The Company’s operations are carried on through our Operating Partnership and its subsidiaries, including our taxable REIT subsidiary. Since the formation of our Operating Partnership, the Company has controlled our Operating Partnership as its general partner and has consolidated its assets, liabilities and results of operations.

In connection with the Offering, on January 19, 2011 the following transactions were completed:

The net proceeds from the Offering were approximately $594.6 million, net of $1.9 million of offering costs prepaid by our Predecessor, including the underwriters’ overallotment option which was exercised in full (after deducting the underwriting discount and commissions and expenses of the Offering and Formation Transactions). We contributed the net proceeds of the Offering to our Operating Partnership in exchange for common units.

Our “Predecessor” is not a legal entity but rather a combination of entities whose assets included entities owned and/or controlled by Ernest S. Rady and his affiliates, including the Ernest Rady Trust U/D/T March 13, 1983 (the “Rady Trust”), which in turn owned (1) controlling interests in entities owning 17 properties and the property management business of American Assets, Inc. (“AAI”) (the “controlled entities”), and (2) noncontrolling interests in entities owning four properties (the “noncontrolled entities”) (the assets described at (1) and (2) are the “Acquired Assets,” and do not include our Predecessor’s noncontrolling 25% ownership interest in Novato FF Venture, LLC, the entity that owns the Fireman’s Fund Headquarters in Novato, California). The Formation Transactions included the acquisition by our Operating Partnership of the (a) Acquired Assets, (b) the entities that own Waikiki Beach Walk (a mixed-use property consisting of a retail portion and a hotel portion) (the “Waikiki Beach Walk entities”) and (c) the entities that own Solana Beach Towne Centre and Solana Beach Corporate Centre (the “Solana Beach Centre entities”) (including our Predecessor’s ownership interest in these entities).

The Formation Transactions enabled us to (1) consolidate the ownership of our property portfolio under our Operating Partnership, (2) succeed to the property management business of AAI, (3) facilitate the Offering, and (4) qualify as a real estate investment trust (a “REIT”) for U.S. federal income tax purposes commencing with the taxable year ending December 31, 2011. As a result of the Formation Transactions, we are a vertically integrated and self-administered REIT with approximately 110 employees providing substantial in-house expertise in asset management, property management, property development, leasing, tenant improvement construction, acquisitions, repositioning, redevelopment and financing.

We determined that our Predecessor was the acquirer for accounting purposes, and therefore the contribution or acquisition by merger of interests in the controlled entities was considered a transaction between entities under common control since our Executive Chairman, Ernest S. Rady or his affiliates, including the Rady Trust, owned the controlling interest in each of the entities comprising our Predecessor, which, in turn, owned a controlling interest in each of the controlled entities. As a

7

American Assets Trust, Inc.

Notes to Consolidated Financial Statements—(Continued)

March 31, 2012

(Unaudited)

result, the acquisition of interests in each of the controlled entities was recorded at our historical cost. The contribution or acquisition by merger of interests in certain of the noncontrolled entities, which include the Waikiki Beach Walk entities and the Solana Beach Centre entities (including our Predecessor’s ownership interest in these noncontrolled entities), was accounted for as an acquisition under the acquisition method of accounting and recognized at the estimated fair value of acquired assets and assumed liabilities on the date of such contribution or acquisition.

Since these transactions occurred on January 19, 2011, the financial condition and results of operations for the entities acquired by us in connection with the Offering and related Formation Transactions are not included in certain historical financial statements. Our results of operations for the three months ended March 31, 2011 reflect the financial condition and results of operation for our Predecessor together with the entities we acquired at the time of the Offering, namely, the Waikiki Beach Walk entities and the Solana Beach Centre entities, as well as entities acquired subsequent to the Offering. We have included the results of operations for the acquired entities in our consolidated statements of operations from the date of acquisition.

As of March 31, 2012, we owned or had a controlling interest in 22 office, retail, multifamily and mixed-use operating properties, the operations of which we consolidate. Additionally, as of March 31, 2012, we owned land at five of our properties that we classify as held for development. A summary of the properties owned by us is as follows:

Retail

Carmel Country Plaza

Carmel Mountain Plaza

South Bay Marketplace

Rancho Carmel Plaza

Lomas Santa Fe Plaza

Solana Beach Towne Centre

Del Monte Center

The Shops at Kalakaua

Waikele Center

Alamo Quarry Market

Office

Torrey Reserve Campus

Solana Beach Corporate Centre

160 King Street

The Landmark at One Market

One Beach Street

First & Main

Lloyd District Portfolio

Multifamily

Loma Palisades

Imperial Beach Gardens

Mariner’s Point

Santa Fe Park RV Resort

Mixed-Use

Waikiki Beach Walk Retail and Hotel

Held for Development

Solana Beach Corporate Centre – Land

Solana Beach – Highway 101 – Land

Sorrento Pointe – Land

Torrey Reserve – Land

Lloyd District Portfolio – Land

8

American Assets Trust, Inc.

Notes to Consolidated Financial Statements—(Continued)

March 31, 2012

(Unaudited)

Basis of Presentation

Our consolidated financial statements include the accounts of the Company, our Operating Partnership and our subsidiaries. The equity interests of other investors in our Operating Partnership are reflected as noncontrolling interests.

All significant intercompany transactions and balances are eliminated in consolidation.

In August 2011, we sold Valencia Corporate Center. We have reclassified our financial statements for all periods prior to the sale to reflect Valencia Corporate Center as discontinued operations. Unless noted otherwise, discussions in these notes pertain to our continuing operations.

The accompanying consolidated financial statements of the Company have been prepared in accordance with the rules applicable to Form 10-Q and include all information and footnotes required for interim financial statement presentation, but do not include all disclosures required under accounting principles generally accepted in the United States (“GAAP”) for annual financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments, except as otherwise noted) considered necessary for a fair presentation have been included.

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that in certain circumstances affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities, and revenues and expenses. These estimates are prepared using management’s best judgment, after considering past, current and expected events and economic conditions. Actual results could differ from these estimates.

Consolidated Statements of Cash Flows—Supplemental Disclosures

The following table provides supplemental disclosures related to the Consolidated Statements of Cash Flows (in thousands):

Significant Accounting Policies

We describe our significant accounting policies in Note 1 to the consolidated financial statements in Item 8 of our Annual Report on Form 10-K for the year ended December 31, 2011. There have been no changes to our significant accounting policies during the three months ended March 31, 2012.

9

American Assets Trust, Inc.

Notes to Consolidated Financial Statements—(Continued)

March 31, 2012

(Unaudited)

Segment Information

Segment information is prepared on the same basis that our management reviews information for operational decision-making purposes. We operate in four business segments: the acquisition, redevelopment, ownership and management of retail real estate, office real estate, multifamily real estate and mixed-use real estate. The products for our retail segment primarily include rental of retail space and other tenant services, including tenant reimbursements, parking and storage space rental. The products for our office segment primarily include rental of office space and other tenant services, including tenant reimbursements, parking and storage space rental. The products for our multifamily segment include rental of apartments and other tenant services. The products of our mixed-use segment include rental of retail space and other tenant services, including tenant reimbursements, parking and storage space rental and operation of a 369-room all-suite hotel.

Reclassifications

Certain items in the consolidated financial statements for prior periods have been reclassified to conform to current classifications.

Recent Accounting Pronouncements

In May 2011, the FASB issued ASU No. 2011-04, Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRSs (“ASU 2011-04”), which amended ASC Topic 820, Fair Value Measurement. ASU 2011-04 clarifies the application of certain existing fair value measurement guidance and expands the disclosures for fair value measurements that are estimated using significant unobservable (Level 3) inputs. ASU 2011-04 is effective for annual and interim reporting periods beginning on or after December 15, 2011. The new guidance is to be adopted prospectively and early adoption is not permitted. The adoption of ASU 2011-04 did not have a significant impact on our financial position, results of operations or cash flows.

In June 2011, the FASB issued ASU No. 2011-05, Presentation of Comprehensive Income (“ASU 2011-05”), which amended ASC Topic 220, Comprehensive Income. ASU 2011-05 eliminates the option to present components of other comprehensive income as part of the statement of changes in equity and requires that all non owner changes in equity be presented either in a single continuous statement of comprehensive income or in two separate but consecutive statements. ASU 2011-05 requires retrospective application and will be effective for interim and annual reporting periods beginning after December 15, 2011. The adoption of ASU 2011-05 did not have significant impact on our disclosures of comprehensive income, since we do not have other comprehensive income.

10

American Assets Trust, Inc.

Notes to Consolidated Financial Statements—(Continued)

March 31, 2012

(Unaudited)

Acquisitions

On January 24, 2012, we completed the acquisition of One Beach Street, consisting of approximately 97,000 rentable square feet in a 3-story fully renovated historic office building located along the Embarcadero in San Francisco’s North Waterfront District. The purchase price was approximately $36.5 million, excluding closing costs of approximately $0.02 million, which was paid with cash on hand.

The fair values assigned to identifiable intangible assets acquired were based on estimates and assumptions determined by management. Using information available at the time the acquisition closed, we allocated the total consideration to tangible assets and liabilities and identified intangible assets and liabilities. The identified intangible assets and liabilities are being amortized over a weighted average life of 7.0 years. We may adjust the preliminary purchase price allocation after obtaining more information about asset valuations and liabilities assumed. The allocation of the purchase price for One Beach Street is as follows (in thousands):

We have included the results of operations for One Beach Street in our consolidated statements of operations from the date of acquisition. For the period of acquisition through March 31, 2012, One Beach Street contributed $0.8 million to total revenue, $0.5 million to operating expenses, $0.3 million to operating income and $0.3 million to net income.

Pro Forma Financial Information

The unaudited financial information in the table below summarizes the combined results of operations of One Beach Street with the historical results of operations of the Company, as though the entity had been acquired on January 1, 2011. The pro forma financial information for the three months ended March 31, 2011 also includes the pro forma results of operations of the Waikiki Beach Walk entities, Solana Beach Centre entities, First & Main, Lloyd District Portfolio and Solana Beach-Highway 101 which were acquired at various times during 2011. The pro forma financial information is presented for informational purposes only and is not indicative of the results of operations that would have been achieved if the acquisitions had taken place on January 1, 2011. The pro forma financial information includes adjustments to depreciation expense for acquired property and equipment, adjustments to amortization charges for acquired intangible assets and liabilities, adjustments to straight-line rent revenue and the removal of the gain on acquisition of the controlling interests of the Solana Beach Centre entities and Waikiki Beach Walk entities for the three months ended March 31, 2011.

11

American Assets Trust, Inc.

Notes to Consolidated Financial Statements—(Continued)

March 31, 2012

(Unaudited)

The following table summarizes the unaudited pro forma financial information (in thousands):

The following summarizes our acquired lease intangibles, which are included in other assets and other liabilities and deferred credits, as of March 31, 2012 and December 31, 2011 (in thousands):

Our portfolio of marketable securities is comprised of debt securities that are classified as trading securities. At March 31, 2012, our marketable securities consisted of investments in mortgage-backed securities issued by the Government National Mortgage Association (“GNMA securities”). We report our trading securities at fair value, using prices provided by independent market participants that are based on observable inputs using market-based valuation techniques (Level 2 of the fair value hierarchy-see Note 5). Gains and losses resulting from the mark-to-market of these securities are recognized as unrealized gains or losses in income. For the three months ended March 31, 2012 and 2011, unrealized losses in our statement of operations, which are included in other income (expense), were $0.3 million for each period. Cumulative unrealized losses were $0.2 million as of March 31, 2012.

12

American Assets Trust, Inc.

Notes to Consolidated Financial Statements—(Continued)

March 31, 2012

(Unaudited)

A fair value measurement is based on the assumptions that market participants would use in pricing an asset or liability. The hierarchy for inputs used in measuring fair value is as follows:

Except as disclosed below, the carrying amounts of our financial instruments approximate their fair value. Financial assets and liabilities whose fair values we measure on a recurring basis using Level 2 inputs consist of GNMA securities and our deferred compensation liability. We measure the fair values of these assets and liability based on prices provided by independent market participants that are based on observable inputs using market-based valuation techniques.

In certain cases, the inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, for disclosure purposes, the level within which the fair value measurement is categorized is based on the lowest level input that is significant to the fair value measurement.

The fair value of our secured notes payable is sensitive to fluctuations in interest rates. Discounted cash flow analysis (Level 2) is generally used to estimate the fair value of our secured notes payable, using rates ranging from 3.9% to 8.3%.

Considerable judgment is necessary to estimate the fair value of financial instruments. The estimates of fair value presented herein are not necessarily indicative of the amounts that could be realized upon disposition of the financial instruments. A summary of the carrying amount and fair value of our financial instruments, all of which are based on Level 2 inputs, is as follows (in thousands):

13

American Assets Trust, Inc.

Notes to Consolidated Financial Statements—(Continued)

March 31, 2012

(Unaudited)

Other assets consist of the following (in thousands):

Lease incentives are amortized over the term of the related lease and included as a reduction of rental income in the statement of operations. The purchase deposit at December 31, 2011 relates to the acquisition of One Beach Street, in San Francisco, California. Such acquisition was completed on January 24, 2012 (Note 2).

Other liabilities and deferred credits consist of the following (in thousands):

Straight-line rent liability relates to leases which have rental payments that decrease over time or one-time upfront payments for which the rental revenue is deferred and recognized on a straight-line basis.

14

American Assets Trust, Inc.

Notes to Consolidated Financial Statements—(Continued)

March 31, 2012

(Unaudited)

The following is a summary of our total debt outstanding as of March 31, 2012 and December 31, 2011 (in thousands):