Janus Investment Fund

Supplement dated January 28, 2014

to Currently Effective Statements of

Additional Information dated October 28, 2013

The following replaces in its entirety the last paragraph found under “Investment Policies and Restrictions Applicable to All Funds” (or “Investment Policies and Restrictions” as applicable) in the “Classification, Investment Policies and Restrictions, and Investment Strategies and Risks” section of the Statement of Additional Information:

For purposes of each Fund’s policies on investing in particular industries, effective December 2013, each Fund will rely primarily on industry or industry group classifications under the Global Industry Classification Standard (“GICS”) developed by Morgan Stanley Capital International with respect to equity investments and classifications published by Barclays for fixed-income investments. Funds with both equity and fixed-income components will rely on industry classifications published by Bloomberg L.P. To the extent that the above classifications are so broad that the primary economic characteristics in a single class are materially different, a Fund may further classify issuers in accordance with industry classifications consistent with relevant SEC staff interpretations. The Funds may change any source used for determining industry classifications without prior shareholder notice or approval.

Please retain this Supplement with your records.