Item 1.01 Entry into a Material Definitive Agreement.
On February 12, 2013, American Capital Mortgage Investment Corp. (the "Company") and American Capital MTGE Management, LLC entered into an Underwriting Agreement (the "Underwriting Agreement") with Barclays Capital Inc., Citigroup Global Markets Inc., Credit Suisse Securities (USA) LLC, Morgan Stanley & Co. LLC and Wells Fargo Securities, LLC, as representatives of the several underwriters named therein (collectively, the "Underwriters"), with respect to (i) the sale by the Company of 20,000,000 shares of the Company's common stock to the Underwriters and (ii) the grant by the Company to the Underwriters of an option to purchase all or part of 3,000,000 additional shares of the Company's common stock (together, the "Shares"). The Company agreed to indemnify the Underwriters against certain specified types of liabilities, including liabilities under the Securities Act of 1933, and to contribute to payments the Underwriters may be required to make in respect of these liabilities. In the ordinary course of business the Underwriters or their respective affiliates have engaged and may in the future engage in various financing, commercial banking and investment banking services with, and provide financial advisory services to, the Company and its affiliates for which they have received or may receive customary fees and expenses. A copy of the Underwriting Agreement is filed as Exhibit 1.1 hereto and is incorporated herein by reference.

Item 9.01. Financial Statements and Exhibits.
On February 15, 2013, Venable LLP delivered an opinion to the Company with respect to the validity of the Shares (the "Opinion"). The Opinion is being filed herewith, and thereby automatically incorporated by reference into the Company's Registration Statement on Form S-3 (No. 333-183772), in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act of 1933.

(d) Exhibits. Exhibit No. Description 1.1 Underwriting Agreement, dated February 12, 2013, by and among American Capital Mortgage Investment Corp. and American Capital MTGE Management, LLC, on the one hand, and Barclays Capital Inc., Citigroup Global Markets Inc., Credit Suisse Securities (USA) LLC, Morgan Stanley & Co. LLC and Wells Fargo Securities, LLC, on the other hand. 5.1 Opinion of Venable LLP, dated February 15, 2013.

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