The 30-year-old, who joined the Dragons in 2008 and signed a new one-year deal in August, played 71 times in the Super League, scoring eight tries.
He joined the club as a second row but spent most of last season as a centre.
Carlaw said: “I am very disappointed to leave and not respecting my contract until the end. But this decision is the best for my family and myself.”
It remains to be seen if Carlaw will seek an NRL contract.