Kellogg is buying protein bar maker RXBar, just days after the cereal company hired a former vitamin executive as CEO.
Kellogg, best known for Frosted Flakes and Pop-Tarts, has struggled to make its cereals and snacks more appealing to Americans who want to avoid sugary processed foods.
Its revenue has suffered, falling every year since 2013.
RXBar says its bars are made with egg whites, fruits and nuts, and exclude dairy, soy or gluten.
Last week, Kellogg Co. hired new CEO Steven Cahillane from vitamin seller Nature's Bounty Co. as it seeks to offer healthier packaged foods.
The Battle Creek, Michigan-based company said Friday it will pay $600 million for RXBar's parent company Chicago Bar Co.
The deal is expected to be completed by the end of the year.