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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 (No. 002-34393)	þ
Pre-Effective Amendment No.	o
Post-Effective Amendment No. 221	þ
and/or
REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940 (No. 811-01879)	þ
Amendment No. 204	þ

(Check appropriate box or boxes.)

JANUS INVESTMENT FUND

(Exact Name of Registrant as Specified in Charter)

  151 Detroit Street, Denver, Colorado 80206-4805  
(Address of Principal Executive Offices) (Zip Code)

Registrant’s Telephone Number, including Area Code: 303-333-3863

Stephanie Grauerholz – 151 Detroit Street, Denver, Colorado 80206-4805
(Name and Address of Agent for Service)

Approximate Date of Proposed Public Offering:

It is proposed that this filing will become effective (check appropriate box):

þ immediately upon filing pursuant to paragraph (b)

o on (date) pursuant to paragraph (b)

o 60 days after filing pursuant to paragraph (a)(1)

o on (date) pursuant to paragraph (a)(1)

o 75 days after filing pursuant to paragraph (a)(2)

o on (date) pursuant to paragraph (a)(2) of rule 485.

If appropriate, check the following box:

o This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, as amended, and the Investment Company Act of 1940, as amended, the Registrant certifies that it meets all of the requirements for effectiveness of this Amendment to its Registration Statement pursuant to Rule 485(b) under the Securities Act of 1933, as amended, and has duly caused this Amendment to its Registration Statement to be signed on its behalf by the undersigned, thereto duly authorized, in the City of Denver, and State of Colorado, on the 2nd day of March, 2015.

JANUS INVESTMENT FUND
By:	/s/ Bruce L. Koepfgen
	Bruce L. Koepfgen, President and
	Chief Executive Officer

     Janus Investment Fund is organized under an Amended and Restated Agreement and Declaration of Trust dated March 18, 2003 (“Declaration of Trust”), a copy of which is on file with the Secretary of State of The Commonwealth of Massachusetts. The obligations of the Registrant hereunder are not binding upon any of the Trustees, shareholders, nominees, officers, agents or employees of the Registrant personally, but bind only the trust property of the Registrant, as provided in the Declaration of Trust of the Registrant. The execution of this Amendment to the Registration Statement has been authorized by the Trustees of the Registrant and this Amendment to the Registration Statement has been signed by an authorized officer of the Registrant, acting as such, and neither such authorization by such Trustees nor such execution by such officer shall be deemed to have been made by any of them personally, but shall bind only the trust property of the Registrant as provided in its Declaration of Trust.

     Pursuant to the requirements of the Securities Act of 1933, as amended, this Amendment to the Registration Statement has been signed below by the following persons in the capacities and on the dates indicated.

Signature	Title	Date
/s/ Bruce L. Koepfgen	President and Chief Executive Officer	March 2, 2015
Bruce L. Koepfgen	(Principal Executive Officer)
/s/ Jesper Nergaard	Vice President, Chief Financial	March 2, 2015
Jesper Nergaard	Officer, Treasurer and Principal
	Accounting Officer (Principal
	Financial Officer and Principal
	Accounting Officer)

Signature	Title	Date
William F. McCalpin*	Chairman and Trustee	March 2, 2015
William F. McCalpin
Alan A. Brown*	Trustee	March 2, 2015
Alan A. Brown
William D. Cvengros*	Trustee	March 2, 2015
William D. Cvengros
James T. Rothe*	Trustee	March 2, 2015
James T. Rothe
William D. Stewart*	Trustee	March 2, 2015
William D. Stewart
Linda S. Wolf*	Trustee	March 2, 2015
Linda S. Wolf

/s/ Stephanie Grauerholz
*By:	Stephanie Grauerholz Attorney-in-Fact
	Pursuant to Powers of Attorney, dated February 6, 2015, incorporated by reference to Exhibit (q)(1) to Post-Effective Amendment No. 218, filed on February 6, 2015

INDEX OF EXHIBITS

Exhibit Number	Exhibit Title
EX-101.INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CAL	XBRL Taxonomy Extension Calculation Linkbase
EX-101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase
EX-101.DEF	XBRL Taxonomy Extension Definition Linkbase