The 28-year-old New Zealand-born forward joined Tigers ahead of the 2020 season from Toulouse Olympique and made 25 appearances.
Hepi, son of former Castleford and Featherstone player Brad Hepi, has also played for Hull KR and Whitehaven.
He has found chances hard to come by at Cas and has moved back to the Championship in the hope of more game time.
Hepi has played four times for the Tigers this year, with his last appearance off the bench against Leeds Rhinos on Easter Monday.
Hepi paid thanks to the Castleford Tigers club, telling the Tigers website: “I would firstly like to thank my teammates past and present for the great memories, especially all the free laughs and good times they provided daily. I wish them all the best for the rest of the season and their careers.
“To the club, staff, supporters and all the people behind the scenes, thank you for everything you’ve done for me and making my time at the club enjoyable. I have loved being a Tiger and look forward to being a supporter for the rest of the season. See you all soon."
The club has thanked Tyla for his efforts as a Castleford player and wish him the best for the future.