Label

Element

Value

Risk/Return:

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Prospectus Date

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Feb. 29, 2012

LargeCap Value Fund (Prospectus Summary): | LargeCap Value Fund

Risk/Return:

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Risk/Return, Heading

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LargeCap Value Fund  

Supplement Text

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Supplement dated September 14, 2012

to the Class R-1, Class R-2, Class R-3, Class R-4 and Class R-5 Shares Prospectus

for Principal Funds, Inc.

dated February 29, 2012

(as supplemented on March 16, 2012, April 23, 2012, June 15, 2012, and July 17, 2012)

This supplement updates information currently in the Prospectus. Retain this supplement with the Prospectus.

FUND SUMMARIES

Investment Strategy, Heading

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Under the Principal Investment Strategies heading, delete the paragraph and substitute:  

Investment Strategy, Narrative

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Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies with large market capitalizations (those with market capitalizations similar to companies in the Russell 1000 ^® Value Index, which as of December 31, 2011 ranged between approximately $117 million and $401.25 billion) at the time of purchase. The Fund invests in value equity securities, an investment strategy that emphasizes buying equity securities that appear to be undervalued. The Fund may actively trade portfolio securities.

LargeCap Value Fund | R-1

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Trading Symbol

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PLSVX

LargeCap Value Fund | R-2

Risk/Return:

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Trading Symbol

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PLVNX

LargeCap Value Fund | R-3

Risk/Return:

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Trading Symbol

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PLVMX

LargeCap Value Fund | R-5

Risk/Return:

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Trading Symbol

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PLVPX

LargeCap Value Fund | R-4

Risk/Return:

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Trading Symbol

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PLVSX