The sale is part of Unilever's ongoing effort to reshape its U.S. portfolio and focus on its core higher-margin personal care business, the company said.
The Anglo-Dutch maker of Ben & Jerry's ice cream, Dove soap and Lipton tea said it would retain a minority stake in the Slim-Fast business, which sells dietary food products, including snack bars and protein meal shakes.
Unilever did not disclose financial terms of the deal, which closed on Thursday. The deal includes the Slim-Fast trademark and global Slim-Fast business portfolio.
The company said in April that it would undertake a strategic review of its North American pasta sauce business, which includes the market-leading Ragu brand, and the troubled Slim-Fast brand, whose sales have tumbled in its biggest market.
Unilever shares were down about 1.5 percent at 2598 pence at 1721 GMT on the London Stock Exchange.
Reporting by Esha Vaish in Bangalore; Editing by Simon Jennings