THIRD AMENDMENT TO EIGHTH AMENDED AND RESTATED STOCKHOLDERS AGREEMENT

This Third Amendment to the Eighth Amended and Restated Stockholders’ Agreement (this “Amendment”) is made as of April 15, 2014 (the “Effective Date”), by and among Five9, Inc., a Delaware corporation (the “Company”), and the Holders (as defined in the Eighth Amended and Restated Stockholders’ Agreement made as of October 28, 2013 (as amended, the Existing Agreement”)) signatory hereto. Capitalized terms used, but not otherwise defined, in this Amendment will have the meanings given to such terms in the Existing Agreement.

WHEREAS, the parties hereto desire to enter into this Amendment in order to amend the Existing Agreement to revise the definition of “Qualified IPO” to mean the closing of the Company’s initial public offering of its common stock pursuant to the Registration Statement on Form S-1 (Registration No. 333-194258).

WHEREAS, under Section 10.1 of the Existing Agreement, the Company, the holders of at least sixty percent of the Registrable Securities, SAPV, ASP, PIV and HWVP may amend provisions of the Existing Agreement.

WHEREAS, the signatories hereto include the Company, the holders of at least sixty percent of the Registrable Securities currently outstanding, SAPV, ASP, PIV and HWVP.

NOW THEREFORE, in consideration of the mutual premises and covenants set forth herein, the parties hereto agree to amend the Existing Agreement as follows:

1.    Section 1(m) is amended and restated to read as follows:

2.     On and after the date hereof, each reference in the Existing Agreement to “this Agreement,” “hereunder,” “hereof,” “herein” or words of like import referring to the Existing Agreement shall mean and be a reference to the Existing Agreement, as amended by this Amendment. This Amendment constitutes the entire agreement among the parties pertaining to the subject matter hereof and supersedes all prior and contemporaneous agreements, understandings, representations or other arrangements, whether express or implied, written or oral, of the parties in connection therewith except to the extent expressly incorporated or

specifically referred to herein. In the event of a conflict between the respective provisions of the Existing Agreement and this Amendment, the terms of this Amendment shall control. Except as specifically amended by the terms of this Amendment, the terms and conditions of the Existing Agreement are and shall remain in full force and effect for all purposes.

3.    This Amendment may be executed in one or more counterparts, each of which shall for all purposes be deemed to be an original and all of which shall constitute the same instrument, but only one of which need be produced.

4.     This Amendment shall be governed by and interpreted under the laws of the State of Delaware as applied to agreements among Delaware residents, made and to be performed entirely within the State of Delaware without reference to the law of conflicts.

IN WITNESS WHEREOF, the undersigned have executed this Amendment as of the date set forth above.