SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

SCHEDULE 13D

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 2)*

SPHERE 3D CORPORATION

(Name of Issuer)

COMMON STOCK, NO PAR VALUE PER SHARE

(Title of Class of Securities)

84841L100

(CUSIP number)

Jennifer M. Pulick

Chief Compliance Officer and General Counsel

Cyrus Capital Partners, L.P.

399 Park Avenue, 39^th Floor

New York, New York 10022

(212) 380-5821

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

December 21, 2015

(Date of Event Which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box  ¨.

(Continued on the following pages)

(Page 1 of 16 Pages)

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (the “Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act.

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This constitutes Amendment No. 2 (“Amendment No. 2”) to the Schedule 13D relating to the shares of Common Stock of Sphere 3D Corporation (the “Issuer” or “Sphere 3D”) filed with the SEC on December 11, 2014 as subsequently amended by Amendment No. 1 filed on August 4, 2015 (as so amended, the “Schedule 13D”) by Cyrus Capital Partners, L.P., a Delaware limited partnership (“Cyrus Capital”), Crescent 1, L.P., a Delaware limited partnership (“CRES”), CRS Master Fund, L.P., a Cayman Islands exempted limited partnership (“CRS”), Cyrus Opportunities Master Fund II, Ltd., a Cayman Islands exempted limited company (“CMFll”), Cyrus Select Opportunities Master Fund, Ltd., a Cayman Islands exempted limited company (“CSOM”), Cyrus Capital Partners GP, L.L.C., a Delaware limited liability company (“Cyrus GP”), Cyrus Capital Advisors, L.L.C., a Delaware limited liability company (“Cyrus Advisors”), FBC Holdings S.à r.l., a Luxembourg private limited liability company (“FBC”) and Mr. Stephen C. Freidheim (each of Cyrus Capital, CRES, CRS, CMFll, CSOM, Cyrus GP, Cyrus Advisors, FBC and Mr. Freidheim, a “Reporting Person” and collectively the “Reporting Persons”). This Amendment No. 2 amends the Schedule 13D as specifically set forth herein. Only those items amended are reported herein. Capitalized terms used in this Amendment No. 2 without being defined herein have the respective meanings given to them in the Schedule 13D.

(a) On December 21, 2015, FBC was issued warrants (the “December 2015 Warrants”) to acquire up to 500,000 Common Shares from Sphere 3D in connection with a US$5 million increase in funding by FBC under the Revolving Credit Agreement. These warrants expire on December 21, 2018. Each whole warrant may be exercised to acquire one Common Share at an exercise price of US$1.54.

(b) Effective on December 21, 2015 and in connection with a US$5 million increase in funding by FBC under the Revolving Credit Agreement and pursuant to the amendment to the New Debentures described below, (i) the Conversion Price applicable to US$9.5 million of outstanding principal balance of New Debentures was reduced from US$8.50 per share to US$3.00 per share and (ii) the Conversion Price applicable to US$10 million of outstanding principal balance of New Debentures was reduced from US$7.50 per share to US$3.00 per share. As a result, the aggregate number of Common Shares issuable upon conversion of all of the outstanding New Debentures increased from 2,450,980 Common Shares to 6,500,000 Common Shares. This filing reflects the fact that all of the New Debentures and the Warrants, 2015 Warrants and December 2015 Warrants are held directly by FBC.

(c) On December 31, 2015, FBC was issued 510,590 Common Shares in lieu of US$786,410 of interest due and payable to FBC by Sphere 3D under the New Debentures. Each of such Common Shares was issued at a price of US$1.54 per share.

(a) On December 21, 2015, FBC was issued the December 2015 Warrants to acquire up to 500,000 Common Shares from Sphere 3D in connection with a US$5 million increase in funding by FBC under the Revolving Credit Agreement. These warrants expire on December 21, 2018. Each whole warrant may be exercised to acquire one Common Share at an exercise price of US$1.54.

(b) Effective on December 21, 2015 and in connection with a US$5 million increase in funding by FBC under the Revolving Credit Agreement and pursuant to the amendment to the New Debentures described below, (i) the Conversion Price applicable to US$9.5 million of outstanding principal balance of New Debentures was reduced from US$8.50 per share to US$3.00 per share and (ii) the Conversion Price applicable to US$10 million of outstanding principal balance of New Debentures was reduced from US$7.50 per share to US$3.00 per share. As a result, the aggregate number of Common Shares issuable upon conversion of all of the outstanding New Debentures increased from 2,450,980 Common Shares to 6,500,000 Common Shares. This filing reflects the fact that all of the New Debentures and the Warrants, 2015 Warrants and December 2015 Warrants are held directly by FBC.

(c) On December 31, 2015, FBC was issued 510,590 Common Shares in lieu of US$786,410 of interest due and payable to FBC by Sphere 3D under the New Debentures. Each of such Common Shares was issued at a price of US$1.54 per share.

Sphere 3D and FBC amended the New Debentures and pursuant to the amendment and on the condition that Sphere 3D provides to FBC subscription agreements evidencing a capital raise by Sphere 3D of at least US$2,750,000 (the “Raise”) through the issuance of Common Shares and/or warrants (i) FBC agreed to fund to Sphere 3D an additional US$5,000,000 pursuant to the terms of the Revolving Credit Agreement upon Sphere 3D’s request (which amount was funded on December 21, 2015), (ii) upon the funding of such US$5 million, the Conversion Price of the entire principal balance of the New Debenture will be reduced to $3.00 per Common Share, (iii) if the maturity date of Sphere 3D’s Silicon Valley Bank credit facility is extended beyond its current maturity date (which would automatically cause the extension of the loans made by FBC to Sphere 3D pursuant to the Revolving Credit Agreement),

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Sphere 3D will issue warrants to FBC to purchase up to 500,000 Common Shares at a price per share equal to 110% of the closing price of the Common Shares on The NASDAQ Global Market immediately prior to the date of any such extension and (iv) any failure to complete the Raise prior to December 15, 2015 would constitute a default under the New Debenture.

The Reporting Persons expect to independently evaluate on an ongoing basis Sphere 3D’s financial condition and prospects and their interest in, and intentions with respect to, Sphere 3D and their investment in the securities of, Sphere 3D, which review may be based on various factors, including whether various strategic transactions have occurred or may occur, Sphere 3D’s business and financial condition, results of operations and prospects, general economic and industry conditions, the securities markets in general and those for Sphere 3D’s securities in particular, as well as other developments and other investment opportunities. Each of the Reporting Persons reserves the right to change its intentions and develop plans or proposals at any time, as it deems appropriate. Each of the Reporting Persons may at any time and from time to time, in the open market, in privately negotiated transactions or otherwise, acquire additional securities of Sphere 3D including Common Shares, dispose of all or a portion of the securities of Sphere 3D, including the Common Shares, that the Reporting Persons now own or may hereafter acquire, and/or enter into derivative transactions with institutional counterparties with respect to Sphere 3D’s securities. In addition, the Reporting Persons may engage in discussions with management of Sphere 3D, members of the board of directors of Sphere 3D, shareholders of Sphere 3D, industry analysts, existing or potential strategic partners or competitors, investment and finance professionals, sources of credit, other investors and other relevant parties concerning the operations, management, composition of Sphere 3D’s board of directors and management, ownership, capital structure, balance sheet management, strategy and future plans of Sphere 3D including the possibility of proposing one of more acquisitions, business combinations, mergers, asset sales, asset purchases or other similar transactions involving Sphere 3D and other third parties.

Except as set forth herein, the Reporting Persons do not have present plans or proposals at this time that relate to or would result in any of the transactions described in subparagraphs (a) through (j) of Item 4 of Schedule 13D. The information set forth in Item 6 of this Schedule 13D is hereby incorporated herein by reference.

(a) and (b) Items 7 through 11 and 13 of each of the cover pages of this Schedule 13D are incorporated herein by reference. Such information is based on 43,333,042 Common Shares outstanding at December 7, 2015 as disclosed in Sphere 3D’s Amendment No. 1 to Form F-3 filed with the Securities and Exchange Commission on December 14, 2015 plus the 510,590 Common Shares which were issued to FBC on December 31, 2015 as reported herein.

(c) Except for the transactions described in Item 4 above, there have been no transactions with respect to the securities of Sphere 3D during the sixty days prior to the date of this Schedule 13D by the Reporting Persons, or to their knowledge, by any executive officer or director of the Reporting Persons.

(d) No other person is known by any Reporting Persons to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, securities of Sphere 3D beneficially owned by any Reporting Person.

(e) Not applicable.

Sphere 3D and FBC amended the New Debentures and pursuant to the amendment and on the condition that Sphere 3D provides to FBC subscription agreements evidencing a capital raise by Sphere 3D of at least US$2,750,000 (the “Raise”) through the issuance of Common Shares and/or warrants (i) FBC agreed to fund to Sphere 3D an additional US$5,000,000 pursuant to the terms of the Revolving Credit Agreement upon Sphere 3D’s request (which amount was funded on December 21, 2015), (ii) upon the funding of such US$5 million, the Conversion Price of the entire principal balance of the New Debenture will be reduced to $3.00 per Common Share, (iii) if the maturity date of Sphere 3D’s Silicon Valley Bank credit facility is extended beyond its current maturity date (which would automatically cause the extension of the loans made by FBC to Sphere 3D pursuant to the Revolving Credit Agreement), Sphere 3D will issue warrants to FBC to purchase up to 500,000 Common Shares at a price per share equal to 110% of the closing price of the Common Shares on The NASDAQ Global Market immediately prior to the date of any such extension and (iv) any failure to complete the Raise prior to December 15, 2015 would constitute a default under the New Debenture.

The Reporting Persons expect to independently evaluate on an ongoing basis Sphere 3D’s financial condition and prospects and their interest in, and intentions with respect to, Sphere 3D and their investment in the securities of, Sphere 3D, which review may be based on various factors, including whether various strategic transactions have occurred or may occur, Sphere 3D’s business and financial condition, results of operations and prospects, general economic and industry conditions, the securities markets in general and those

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for Sphere 3D’s securities in particular, as well as other developments and other investment opportunities. Each of the Reporting Persons reserves the right to change its intentions and develop plans or proposals at any time, as it deems appropriate. Each of the Reporting Persons may at any time and from time to time, in the open market, in privately negotiated transactions or otherwise, acquire additional securities of Sphere 3D including Common Shares, dispose of all or a portion of the securities of Sphere 3D, including the Common Shares, that the Reporting Persons now own or may hereafter acquire, and/or enter into derivative transactions with institutional counterparties with respect to Sphere 3D’s securities. In addition, the Reporting Persons may engage in discussions with management of Sphere 3D, members of the board of directors of Sphere 3D, shareholders of Sphere 3D, industry analysts, existing or potential strategic partners or competitors, investment and finance professionals, sources of credit, other investors and other relevant parties concerning the operations, management, composition of Sphere 3D’s board of directors and management, ownership, capital structure, balance sheet management, strategy and future plans of Sphere 3D including the possibility of proposing one of more acquisitions, business combinations, mergers, asset sales, asset purchases or other similar transactions involving Sphere 3D and other third parties.

The Reporting Persons may be deemed to be a “group” pursuant to Section 13(d)(3) of the Act. Neither the filing of this Schedule 13D nor any of its contents shall be deemed to constitute an admission that the Reporting Persons or any of their respective affiliates are the beneficial owners of any Common Stock beneficially owned by any of the Reporting Persons for purposes of Section 13(d) of the Act, the rules promulgated thereunder or for any other purpose.

The information set forth in Item 4 of this Schedule 13D is hereby incorporated by reference.

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SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, each of the undersigned hereby certifies that the information set forth in this statement is true, complete and correct.

EXECUTED as a sealed instrument this 4th day of January, 2016.

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