The building society has signed a 12-month deal with the newspaper and its logo will now appear on the front page of the weekly section, which is published within the newspaper.
The deal was brokered between Mail Connected, the paper's commercial arm, media agency MPG, and Chris Ladd, marketing planning manager at Nationwide.
The Mail on Sunday has sold other section sponsorships to drive up revenues, including its Enterprise Zone section to T Mobile.
Sponsored standalone supplements are not uncommon in newspapers, and The Guardian and the Financial Times are among those that have published them.
However, sponsored sections of newspapers are less common.
In 2009, the Telegraph trialled a supplement called The Friday sponsored by Gordon's gin.