SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person* BAIN CAPITAL INVESTORS LLC (Last) (First) (Middle) JOHN HANCOCK TOWER 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 06/11/2014	3. Issuer Name and Ticker or Trading Symbol Trinseo S.A. [ TSE ]
		4. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)	5. If Amendment, Date of Original Filed (Month/Day/Year)
			6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Ordinary Shares	37,269,567	I	See Footnotes(1)(2)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

1. Name and Address of Reporting Person* BAIN CAPITAL INVESTORS LLC (Last) (First) (Middle) JOHN HANCOCK TOWER 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* BCIP Trust Associates IV-B, L.P. (Last) (First) (Middle) JOHN HANCOCK TOWER 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

Explanation of Responses:

1. Represents ordinary shares of Trinseo S.A. held by Bain Capital Everest Manager Holding SCA ("BCEM Holding") whose general partner is Bain Capital Everest Manager S.a r.l. ("BCEM"). All of the outstanding share capital of BCEM is held by Bain Capital Europe Fund III, L.P. ("Europe Fund III") and, in that capacity, Europe Fund III has the power to appoint the managers of BCEM. Bain Capital Investors, LLC ("BCI") is the general partner of Bain Capital Partners Europe III, L.P., which is the general partner of Europe Fund III. By virtue of these relationships, BCI may be deemed to share voting and dispositive power with respect to the shares held by BCEM Holding. BCI disclaims beneficial ownership of the shares held by BCEM Holding except to the extent of its pecuniary interest therein.

2. In addition to being the general partner of Bain Capital Partners Europe III, L.P., which is the general partner of Europe Fund III, BCI is the general partner of Bain Capital Partners X, L.P., which is the general partner of Bain Capital Fund X, L.P. BCI is also the managing general partner of BCIP Associates IV, L.P., BCIP Associates IV-B, L.P., BCIP Trust Associates IV, L.P. and BCIP Trust Associates IV-B, L.P. By virtue of these relationships, BCI may be deemed to share voting and dispositive power with respect to the shares of Trinseo S.A. held by BCEM Holding that may be deemed to be beneficially owned by the Bain Capital funds. BCI and each of the Bain Capital funds disclaims beneficial ownership of the shares owned by BCEM Holding except to the extent of its pecuniary interest therein.

Remarks:

Form 2 of 2

	/s/ Stephen Zide	06/11/2014
	** 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 5 (b)(v).
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