Exhibit 31.2



American Capital Agency Corp.

Certification Pursuant to Section 302(a)

of
the Sarbanes-Oxley Act Of 2002



I, John R. Erickson, certify
that:



| | 1. | I have reviewed this Quarterly Report on Form 10-Q of American Capital Agency Corp.;
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| | 2. | Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in
light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;
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| | 3. | Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial
condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;
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| | 4. | The registrants other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act
Rules 13a-15(e) and 15d-15(e)) for the registrant and have:
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| | a) | Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material
information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;
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| | b) | (Reserved);
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| | c) | Evaluated the effectiveness of the registrants disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the
disclosure controls and procedures as of the end of the period covered by this report based on such evaluation; and
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| | d) | Disclosed in this report any change in the registrants internal control over financial reporting that occurred during the registrants most recent fiscal
quarter that has materially affected, or is reasonably likely to materially affect, the registrants internal control over financial reporting; and
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| | 5. | The registrants other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the
registrants auditors and the audit committee of registrants board of directors:
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| | a) | All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely
affect the registrants ability to record, process, summarize and report financial information; and
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| | b) | Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrants internal control over financial
reporting.
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|                       |  |     |  |                                                                      
|---------------------- |  | --- |  | ---------------------------------------------------------------------
|Date: October 22, 2009 |  | By: |  | /s/    JOHN R.
ERICKSON                                              
|                       |  |     |  | John R. Erickson Executive
Vice President and Chief Financial Officer