The 28-year-old utility is now in his 10th season in the NRL, only the third player after Stacey Jones and Awen Guttenbeil to reach the milestone for the Warriors.
Hohaia told his team-mates about his decision this morning.
Warriors chief executive Wayne Scurrah said the club was reluctant to see Hohaia leave.
“We had an option for next year but it was too early for us to make a decision on it,” he said.
“Lance asked whether he would be able to have a look around for opportunities in the meantime and the St Helens offer came up soon after.
“He’s in his testimonial year with us and in view of the fantastic contribution he has made to the Warriors we have allowed him to pursue his plans. It’s a brilliant contract for him and I know everyone at the club, our members and all fans will wish him all the best.”
Warriors coach Ivan Cleary said while Hohaia would be leaving at the end of the season, he would continue to have a critical role in the team.