Dorn made his announcement less than 24 hours after scoring a hat-trick on his return from a two-month lay-off, due to a hamstring injury, in Tigers’ 52-12 win at Leeds Rhinos.
The 33-year-old Australian moved to Super League 11 years ago and is in his second spell at Castleford.
He has also played for Salford and London, as well as NRL clubs Northern Eagles, Manly Sea Eagles and Sydney Roosters.
“It will be with a heavy heart when I finish here, but it’s a great club I am finishing at and I’m really excited that my last game will be for this great club.” Dorn said.
“It’s a completely different club from when I was here the first time [in 2008] and I think we’ve all played a part in where the club is at now, Daryl [Powell] from the top with his coaching staff and the players that have come and gone. Everybody is shaping the club in some was shape or form, I think.”