Sargent, 30, joined the Tigers part way through the 2008 season and has since made 49 appearances for the club.
He said: “I have enjoyed my time with the Tigers but with my current contract ending this season I feel that it’s a good time to return home. Kiri and I had a new baby in November and I’m sure that people will appreciate that we want to be around our family in Australia.
“But in the meantime I’ll be doing my very best for the rest of the season to help the Tigers climb the ladder and into the play offs.”
Sargent moved to the UK after a season and a half at Newcastle, which followed spells with Melbourne and North Queensland in the NRL.
Tigers coach Terry Matterson said: “Mitch joined us at a tough time and his experience helped move the club forward. He has proved a great acquisition and has been a fine ambassador for the Tigers both on and off the field. We wish him, Kiri and their young son London all the best and I’m sure that he’ll be looking to go out in the best possible manner.”