The 30-year old has played a total of 162 games in the NRL after making his debut in 2008, including stints for the Panthers, Eels and Cronulla.
Additionally, Paulo has made 11 appearances for Samoa and led USA in the 2013 World Cup as skipper.
Saints head coach Justin Hoolbrook has monitored Paulo over an extended period and admired the traits he will bring to the team.
“He has a high skill level, with good vision, and will be a good addition to the squad next season.”
Paulo was excited about the opportunity to take his talents to England and become a part of the Saints’ successful culture.
“The decision to leave the NRL and come over to the UK is one I am really excited about,” he told saintsrlfc.com
“It was a choice that was made easier too when I knew I was coming over to a great club like St. Helens.
“They have been a successful club for many years and with the culture they have built over time I just wanted to be a part of it.
“The timing felt right with a young family too and it will be great to link up with some old friends there.
“I’m looking forward to meeting the Saints fans and showing what I can do.”