UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549





FORM 10-K/A

Amendment No. 1







|x | ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
|- | ------------------------------------------------------------------------------------

For the fiscal year ended December 31, 2012

OR



| ̈ | TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
|- | ----------------------------------------------------------------------------------------

For the transition period from
 to

Commission File Number: 001-08896





CAPSTEAD
MORTGAGE CORPORATION

(Exact name of registrant as specified in its charter)







|                                                               |  |                                     
|-------------------------------------------------------------- |  | ------------------------------------
|Maryland                                                       |  | 75-2027937                          
|(State or other jurisdiction of
incorporation or organization) |  | (I.R.S. Employer Identification No.)
|                                                               | 
|8401 North Central Expressway, Suite 800, Dallas, TX           |  | 75225-4404                          
|(Address of principal executive offices)                       |  | (Zip Code)                          

Registrants telephone number, including area code: (214) 874-2323

Securities registered pursuant to Section 12(b) of the Act:



|                                                                         |  |                                     
|------------------------------------------------------------------------ |  | ------------------------------------
|Title of Each Class                                                      |  | Name of Exchange on Which Registered
|Common Stock ($0.01 par value)                                           |  | New York Stock Exchange             
|$1.60 Cumulative Preferred Stock, Series A ($0.10 par value)             |  | New York Stock Exchange             
|$1.26 Cumulative Convertible Preferred Stock, Series B ($0.10 par value) |  | New York Stock Exchange             





Indicate by check mark if the Registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.    x  Yes     ̈  No

Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the
Act.     ̈  Yes    x  No

Indicate by check mark whether the Registrant (1) has filed all documents and reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12
months, 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 Web site, 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 Registrant was required to submit and post such
files).    x  Yes     ̈  No

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of the Registrants knowledge, in
definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.   ̈

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 definition of accelerated filer and large accelerated filer in Rule 12b-2 of the Exchange Act (check one)



|                        |  |   |  |                           |  |  
|----------------------- |  | - |  | ------------------------- |  | -
|Large accelerated filer |  | x |  | Accelerated filer         |  |  ̈
|                        |  |   | 
|Non-accelerated filer   |  |  ̈ |  | Smaller Reporting Company |  |  ̈

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

At June 29, 2012 the aggregate market value of the common stock held by nonaffiliates was $1,335,075,485.

Number of shares of Common Stock outstanding at May 2, 2013: 95,559,871









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EXPLANATORY NOTE

This Amendment No. 1 to the Annual Report on Form 10-K for the year ended December 31, 2012 of Capstead Mortgage Corporation (the Annual Report) is filed for the purpose of filing a
complete copy of the charter of Capstead Mortgage Corporation as an exhibit hereto, which is being updated to include immaterial amendments not previously filed. Except as described above, no other changes have been made to the Annual Report. This
Amendment No. 1 to the Annual Report continues to speak as of the date of the Annual Report and does not update the disclosures contained in the Annual Report to reflect any events that occurred at a date subsequent to the filing of the Annual
Report. The filing of this Amendment No. 1 to the Annual Report is not a representation that any statements contained in items of the Annual Report other than that information being amended are true or complete as of any date subsequent to the
date of the Annual Report.

PART IV



|ITEM 15. | EXHIBITS AND FINANCIAL STATEMENT SCHEDULES
|-------- | ------------------------------------------

(a)

3. Exhibits:

Exhibits unaffected by this Amendment No. 1 have been omitted.



|              |  |                                                                                                                                                                      
|------------- |  | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------
|ExhibitNumber |  | Description                                                                                                                                                          
|              | 
|3.1           |  | Charter, including Articles of Incorporation, Articles Supplementary for each series of preferred shares and all other amendments to such Articles of
Incorporation.*
|              | 
|31.1          |  | Certification pursuant to Section 302(a) of the Sarbanes-Oxley Act of 2002.*                                                                                         
|              | 
|31.2          |  | Certification pursuant to Section 302(a) of the Sarbanes-Oxley Act of 2002.*                                                                                         
|              | 
|32            |  | Certification pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.*                                                                                            



|* | Furnished herewith.
|- | -------------------



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Signatures

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, Capstead has duly caused this report to be signed on its behalf by the undersigned, thereunto duly
authorized.



|                   |  |     |  |                                                                                                  
|------------------ |  | --- |  | -------------------------------------------------------------------------------------------------
|                   |  |     |  | CAPSTEAD MORTGAGE CORPORATION Registrant                                                         
|                   |  |    
|Date: May 13, 2013 |  | By: |  | /s/ ANDREW F. JACOBS                                                                             
|                   |  |     |  | Andrew F. Jacobs                                                                                 
|                   |  |     |  | Chief Executive Officer and President                                                            
|                   |  |    
|Date: May 13, 2013 |  | By: |  | /s/ PHILLIP A. REINSCH                                                                           
|                   |  |    
|                   |  |     |  | Phillip A. Reinsch                                                                               
|                   |  |     |  | Executive Vice President and Chief Financial Officer (Principal Financial and Accounting Officer)



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INDEX TO EXHIBITS



|              |  |                                                                                                                                                                      
|------------- |  | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------
|ExhibitNumber |  | Description                                                                                                                                                          
|              | 
|3.1           |  | Charter, including Articles of Incorporation, Articles Supplementary for each series of preferred shares and all other amendments to such Articles of
Incorporation.*
|              | 
|31.1          |  | Certification pursuant to Section 302(a) of the Sarbanes-Oxley Act of 2002.*                                                                                         
|              | 
|31.2          |  | Certification pursuant to Section 302(a) of the Sarbanes-Oxley Act of 2002.*                                                                                         
|              | 
|32            |  | Certification pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.*                                                                                            



|* | Furnished herewith.
|- | -------------------