Moa has spent the past four years at the Roosters after stints with Hull FC and Cronulla.
The New Zealand international said: “I am very excited and proud to join the Catalans team.
“After careful consideration, my family and I are pleased to call Perpignan our new home and we look forward to experiencing the French culture and lifestyle.
“Having done some travelling through France previously, we know we have a lot to look forward to.”
“I am very much looking forward to playing the best football I can for the team and contributing to creating a positive culture at the club.
“It is an exciting time ahead and I thank the club for giving me and my family the opportunity to be a part of it.”
Moa, 30, started his career at Cronulla in 2008 before joining Hull FC where he spent four seasons, making 78 appearances and scoring seven tries.
Catalans Dragons Head coach Laurent Frayssinous said: “I’m delighted to sign a player of Sam’s calibre.
“He is considered by his former coaches and by his opponents as a tough player on the field and is exemplary off the field.
“He is extremely motivated to bring his experience here and to help the club to build a competitive team on and off the field.”
Club CEO Christophe Jouffret concluded: “To recruit a leader such as Sam is a great news for the club.
“His experience, his winning culture and his knowledge of the Super League and the international stage will make him a leader of our team.
“His professionalism off the field is also recognised by all and I’m sure he will be a key player of our 2017 pack.”