Back-rower Ben Sagar will be the third Keighley player to hang up his boots at the end of the season.
Sagar, 27, has made 84 appearances for the Cougars in two spells at the club and previously spent two years out of the game following the birth of his daughter and work commitments.
At the weekend, captain James Feather played his final home game for the club after 15 years of service.
Forward Neil Cherryholme is also retiring at the end of the season.
Keighley round-off the League 1 Super 8s with a trip to Barrow and still have hopes of securing a play-off place and the chance of promotion to the Championship.