Fulton, 25, arrived at the Galpharm Stadium earlier this season as a replacement for Todd Carney, but he is now set for a return down under.
Giants managing director Richard Thewlis said: Liam was always a short-term option for us after the Todd Carney deal fell through.
“He has been great to have around but he has unfulfilled ambitions in the Australian NRL to pursue.
“I know he has enjoyed learning from Nathan Brown and will continue to play a big part in the games we have left.”
Fulton won the NRL with Wests in 2005, and made 76 appearances for the club before his move to the UK to help ease the Tigers’ salary cap worries.