FORM 4
[ ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).         	UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES
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                      	Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	                      	

1. Name and Address of Reporting Person *

Nolan Mangini Siobhan	2. Issuer Name and Ticker or Trading Symbol

CASTLIGHT HEALTH, INC. [ CSLT ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable)

_____ Director                      _____ 10% Owner
__ X __ Officer (give title below)      _____ Other (specify below)
CFO & Treasurer	
(Last)          (First)          (Middle)

C/O CASTLIGHT HEALTH, INC., 150 SPEAR ST., SUITE 400	3. Date of Earliest Transaction (MM/DD/YYYY)

8/16/2017		
(Street)

SAN FRANCISCO, CA 94105
(City)        (State)        (Zip)	4. If Amendment, Date Original Filed (MM/DD/YYYY)

 	6. Individual or Joint/Group Filing (Check Applicable Line)

_ X _ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person	

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned	
1.Title of Security
(Instr. 3)	2. Trans. Date	2A. Deemed Execution Date, if any	3. Trans. Code
(Instr. 8)	4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)	5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)	
			Code	V	Amount	(A) or (D)	Price				
Class B Common Stock  	8/16/2017  	 	M (1)	  	2500  	A	$0  	41622  	D  	 	
Class B Common Stock  	8/16/2017  	 	M (2)	  	1875  	A	$0  	43497  	D  	 	
Class B Common Stock  	8/16/2017  	 	M (3)	  	62500  	A	$0  	105997  	D  	 	
Class B Common Stock  	8/17/2017  	 	S	  	28414   (4)	D	$3.6635   (5)	77583  	D  	 	
Class B Common Stock  	8/17/2017  	 	M (6)	  	578  	A	$0  	78161  	D  	 	
Class B Common Stock  	8/18/2017  	 	S	  	225   (4)	D	$3.67  	77936  	D  	 	

Table II - Derivative Securities Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities)	
1. Title of Derivate Security
(Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Trans. Date	3A. Deemed Execution Date, if any	4. Trans. Code
(Instr. 8)	5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)	6. Date Exercisable and Expiration Date	7. Title and Amount of Securities Underlying Derivative Security
(Instr. 3 and 4)	8. Price of Derivative Security
(Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)	
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares					
Restricted Stock Units  	$0   (7)	8/16/2017  	 	M   (1)	  	  	2500   	  (8)	  (8)	Class B common stock  	2500  	$0  	22500  	D  	 	
Restricted Stock Units  	$0   (7)	8/16/2017  	 	M   (2)	  	  	1875   	  (9)	  (9)	Class B Common Stock  	1875  	$0  	18750  	D  	 	
Restricted Stock Units  	$0   (7)	8/16/2017  	 	M   (3)	  	  	62500   	  (10)	  (10)	Class B Common Stock  	62500  	$0  	187500  	D  	 	
Restricted Stock Units  	$0   (7)	8/17/2017  	 	M   (6)	  	  	578   	  (11)	  (11)	Class B Common Stock  	578  	$0  	2891  	D  	 	

Explanation of Responses:	
(1) 	Release and settlement of restricted stock units ("RSUs") granted to the Reporting Person on November 16, 2015, the grant of which was previously reported by the Reporting Person on a Form 3.	
(2) 	Release and settlement of RSUs granted to the Reporting Person on February 26, 2016, the grant of which was previously reported by the Reporting Person on a Form 3.	
(3) 	Release and settlement of RSUs granted to the Reporting Person on July 8, 2016, the grant of which was previously reported by the Reporting Person on a Form 4.	
(4) 	All of these shares were sold to cover taxes and fees due upon the release and settlement of the RSU's. The Reporting Person did not sell or otherwise dispose of any of the shares reported on this Form 4 for any reason other than to cover required taxes and fees.	
(5) 	Represents the weighted average sales price per share. The shares sold at prices ranging from $3.50 to $3.875 per share. Full information regarding the number of shares sold at each price shall be provided upon request to the staff of the U.S. Securities and Exchange Commission, the Issuer, or a security holder of the Issuer.	
(6) 	Release and settlement of RSUs granted to the Reporting Person on November 17, 2014, the grant of which was previously reported by the Reporting Person on a Form 4.	
(7) 	Each RSU represents a contingent right to receive 1 share of the Issuer's Class B common stock upon settlement for no consideration.	
(8) 	25% of the RSUs vested on November 16, 2016 and the remainder vest quarterly over three years thereafter in equal installments. Shares of the Issuer's Class B common stock will be delivered to the Reporting Person following vesting, at which time shares will be sold by the Reporting Person to cover any tax withholding obligations.	
(9) 	25% of the RSUs vested on February 16, 2017 and the remainder will vest quarterly over three years thereafter in equal installments. Shares of the Issuer's Class B common stock will be delivered to the Reporting Person following vesting, at which time shares will be sold by the Reporting Person to cover any tax withholding obligations.	
(10) 	25% of the RSUs vested on August 16, 2017 and the remainder will vest quarterly over three years thereafter in equal installments. Shares of the Issuer's Class B common stock will be delivered to the Reporting Person following vesting, at which time shares will be sold by the Reporting Person to cover any tax withholding obligations.	
(11) 	25% of the RSUs vested on November 17, 2015 and the remainder will vest quarterly over three years thereafter in equal installments. Shares of the Issuer's Class B common stock will be delivered to the Reporting Person following vesting, at which time shares will be sold by the Reporting Person to cover any tax withholding obligations.	

Reporting Owners	
Reporting Owner Name / Address	Relationships	
	Director	10% Owner	Officer	Other	
Nolan Mangini Siobhan
C/O CASTLIGHT HEALTH, INC.
150 SPEAR ST., SUITE 400
SAN FRANCISCO, CA 94105			CFO & Treasurer		

Signatures		
/s/ Jennifer Chaloemtiarana, by power of attorney		8/18/2017	
** Signature of Reporting Person		Date

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.	
*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).	
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).	
Note:	File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.	
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.