Former All Black Mils Muliaina will play in the inaugural US domestic rugby competition.
Muliaina, the second All Black to reach 100 Test caps and 2011 World Cup winner, has signed a one year deal with San Francisco.
The 35-year-old had an extensive Super Rugby career with the Blues and the Chiefs, followed by spells in Japan, Ireland and Italy.
"We are excited to bring Mils to the United States and look forward to seeing him in San Francisco's colors this spring," said PRO Rugby's Director of Rugby Steve Lewis.
"He has a terrific track record and we are sure he will bring great knowledge and experience to both the league and our younger players in what are exciting times for American rugby."
"I am delighted and looking forward to being part of Rugby history in the States" said Muliaina.
"From initially just going to study in San Francisco to now being able to continue to play rugby, I am grateful that Pro Rugby and Life West Chiropractic have provided me the opportunity to do both. I'm excited to be able to play in the San Francisco Bay area and to work along side and share my experience with some talented young players."
PRO rugby kicks off on April 17th, 2016 with San Francisco v Sacramento at Bonney Field.