Hull FC loose-forward Danny Washbrook has joined Wakefield on a three-year deal, while the East Yorkshire side have released Ewan Dowes, Cameron Phelps and Epalahame Lauaki.
Following Sunday's 42-10 eliminator defeat by Leeds, the quartet have failed to gain new contracts at Hull.
Prop Dowes, 30, had been at the club for nine years and is set to join coach Richard Agar and Washbrook at Wildcats.
Full-back Phelps, 26, had been at Hull for six months.
Tonga forward Lauaki, 27, was a Black & Whites player for three years while 26-year-old Washbrook had been there for six years.
Hull duo Sean Long and Craig Fitzgibbon have retired as expected.
Washbrook told his old side's website: "At this stage in my career, I felt the time was right for a change and a new challenge for me to kick into gear."