KCG Kcg Holdings Class A

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1,457,266 Class A Common Shares and 570,267 Warrant Shares reported in the table above are held directly by the Schuler Family GST Trust. Stephen G. Schuler may be deemed, for purposes of Rule 13d-3 under the Securities Exchange Act of 1934, as amended, to share voting and dispositive power with respect to these securities. Neither the filing of this Schedule 13D nor any of its contents shall be deemed to constitute an admission by the Reporting Person that he is the beneficial owner of any of such securities for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or for any other purpose.

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1,457,266 Class A Common Shares and 570,267 Warrant Shares reported in the table above are held directly by the Schuler Family GST Trust. Mary Jo Schuler may be deemed, for purposes of Rule 13d-3 under the Securities Exchange Act of 1934, as amended, to share voting and dispositive power with respect to these securities. Neither the filing of this Schedule 13D nor any of its contents shall be deemed to constitute an admission by the Reporting Person that she is the beneficial owner of any of such securities for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended, or for any other purpose.

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Introduction

This Amendment No. 5 (this “Amendment No. 5”) amends Amendment No. 4 dated February 3, 2014 (“Amendment No. 4”), Amendment No. 3 dated December 31, 2013 (“Amendment No. 3”), Amendment No. 2 dated December 9, 2013 (“Amendment No. 2”) and Amendment No. 1 dated November 1, 2013 (“Amendment No. 1”) to the statement on Schedule 13D dated July 1, 2013 (the “Original Statement” and, together with Amendment No. 1, Amendment No. 2, Amendment No. 3, Amendment No. 4 and this Amendment No. 5, this “Schedule 13D”) relating to the Class A common stock, par value $0.01 per share (the “Class A Common Shares”), of KCG Holdings, Inc., a Delaware corporation (“KCG Holdings”). Except as specifically provided herein, this Amendment No. 5 does not modify any of the information previously reported in the Original Statement. Any capitalized terms used in this Amendment No. 5 and not otherwise defined herein shall have the respective meanings ascribed to such terms in the Original Statement.

This Amendment No. 5 reflects transactions and developments through March 3, 2014 relating to the Reporting Persons’ holdings of Class A Common Shares. In particular, this Amendment No. 5 is being filed to reflect (i) the sale of 3,000,000 Class A Common Shares by Serenity Investments, LLC, a limited liability company organized under the laws of the state of Alaska (“Serenity”), in a private transaction with Jefferies LLC, (ii) in connection with such sale, Serenity’s agreement not to sell any Class A Common Shares during the six month period after the date thereof and (iii) the termination of the previously-disclosed Rule 10b5-1 Plan.

There has been no change to the information disclosed in Item 1 of the Original Statement.

There has been no change to the information disclosed in Item 2 of the Original Statement.

There has been no change to the information disclosed in Item 3 of the Original Statement.

There has been no change to the information disclosed in Item 4 of the Original Statement, and the information disclosed in Item 4 of Amendment No. 1 is hereby superseded.

Item 5 of the Schedule 13D is hereby amended and restated in its entirety as follows:

(a) - (b) With respect to Serenity, Stephen G. Schuler and Mary Jo Schuler, this Schedule 13D relates to the beneficial ownership of 11,303,933 Class A Common Shares, which include (i) 7,161,251 Class A Common Shares and (ii) 4,142,682 Warrant Shares. Such 11,303,933 shares represent 8.7% of the outstanding Class A Common Shares (based on a total of 129,849,008 Class A Common Shares outstanding, which consists of (i) an estimated 125,706,326 Class A Common Shares outstanding as of February 27, 2014, according to information filed by KCG Holdings on March 3, 2014, and (ii) 4,142,682 Warrant Shares). All of these Class A Common Shares and Warrant Shares are held by Serenity. Stephen G. Schuler and Mary Jo Schuler separately hold equity interests in Serenity that together represent a controlling equity interest in Serenity. Each of Serenity, Stephen G. Schuler and Mary Jo Schuler may be deemed to share voting and dispositive power with respect to these securities. Each of Stephen G. Schuler and Mary Jo Schuler disclaims beneficial ownership of these securities except to the extent of his or her pecuniary interest therein. Neither the filing of this Schedule 13D nor any of its contents shall be deemed to constitute an admission by Stephen G. Schuler or Mary Jo Schuler that he or she is the beneficial owner of any of such securities referred to herein for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or for any other purpose.

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Solely with respect to Stephen G. Schuler and Mary Jo Schuler, this Schedule 13D also relates to the beneficial ownership of an additional 2,027,533 Class A Common Shares, which include (i) 1,457,266 Class A Common Shares and (ii) 570,267 Warrant Shares. Together with the 11,303,933 shares described in the preceding paragraph, these shares represent 10.2% of the outstanding Class A Common Shares (based on a total of 130,419,275 Class A Common Shares outstanding, which consists of (i) an estimated 125,706,326 Class A Common Shares outstanding as of February 27, 2014, according to information filed by KCG Holdings on March 3, 2014, and (ii) 4,712,949 Warrant Shares). All of the 2,027,533 Class A Common Shares and Warrant Shares are held by the Schuler Family GST Trust. Stephen G. Schuler and Mary Jo Schuler may be deemed, for purposes of Rule 13d-3 under the Exchange Act, to share voting and dispositive power with respect to these securities. Stephen G. Schuler and Mary Jo Schuler disclaim beneficial ownership of these securities. Neither the filing of this Schedule 13D nor any of its contents shall be deemed to constitute an admission by Stephen G. Schuler or Mary Jo Schuler that he or she is the beneficial owner of any of such securities for purposes of Section 13(d) of the Exchange Act or for any other purpose.

(c) On March 3, 2014, Serenity sold 3,000,000 Class A Common Shares at a price of $11.00 per share to Jefferies LLC in a private transaction. In connection therewith, Serenity agreed not to sell any Class A Common Shares during the six month period after the date thereof. Serenity reserves the right to seek to amend this restriction. In addition, as described in Item 4 of Amendment No. 1, Serenity entered into a Rule 10b5-1 Plan on November 1, 2013 (the “Rule 10b5-1 Plan”) with respect to 2,200,000 Class A Common Shares, of which 500,000 Class A Common Shares remain available for sale thereunder. On March 3, 2014, the Rule 10b5-1 Plan was terminated. No Reporting Person has effected any other transaction in the Class A Common Shares or Warrant Shares since the filing of Amendment No. 4.

(d) To the knowledge of the Reporting Persons, no other person has the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the Class A Common Shares or Warrant Shares covered by this Schedule 13D.

(e) Not applicable.

Except as disclosed in paragraph (c) of Item 5 of this Amendment No. 5, no Reporting Person has any contracts, arrangements, understandings or relationships with respect to any securities of KCG Holdings.

There has been no change to the information disclosed in Item 7 of the Original Statement.

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SIGNATURES

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

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