The comedy stars Dakota Johnson as a single mother and Nat Faxon as her hapless brother who helps raise his niece.
Stults will play a similarly single father who becomes romantically interested in Kate (Johnson), according to TVLine. He will first appear in the show's Halloween episode on October 30.
The 34-year-old actor recently played the lead role of Major Walter Sherman on short-lived Bones spinoff The Finder, starring opposite the late Michael Clarke Duncan.
He has also appeared on How I Met Your Mother and 7th Heaven, while his film credits include 2005's Wedding Crashers and 2011's J. Edgar.
Ben and Kate premieres on September 25 at 8.30 / 7.30c on Fox. ITV2 will air the sitcom in the UK.
> Fox's Ben and Kate casts Rob Corddry for guest appearance
> How I Met Your Mother casts Saturday Night Live star Abby Elliott
Watch a clip from Ben and Kate below: