The former Sydney Rooster will join Aviva Premiership side London Irish at the end of the season. Sa has so far made 55 Super League appearances, scoring 18 tries since his arrival in 2010.
Sa said: “It was very difficult to leave the Dragons. I have really enjoyed my time here during the last three years, in this club who goes stronger and better.
“I am leaving Perpignan for family reasons. My wife is English, she is pregnant and wants to get closer to her family.”
Catalan coach Trent Robinson praised Sa for the effort he has put into the club.
He said: “He has been a great player for us over the last three years, and I have valued his character and strength both on and off the field. We are both looking forward to a great finish of his time in France.”