Tu'ipulotu, who has played at two World Cup Finals for Tonga, in 1999 and 2007, has previously played for Pontypool, Caerphilly, Newport Gwent Dragons and in the Far East with Yokogawa.
The 32-year-old, who is 6ft 1in and weighs 15st 6lb, played 65 games for Newport Gwent Dragons between 2003 and 2006.
Tu'ipulotu joined Plymouth in 2009 and has been a star performer over the last two seasons at Brickfields, recently picking up the player of the year award.
Head Coach Richard Hill said: "I have tracked Sione since he was at the Dragons and will are confident he can make a big impact at Sixways and will join us to primarily play as a centre.
"Sione has been one of the key performers for Plymouth Albion the last two seasons. He is a very powerful centre and in the Aviva Premiership you need those types of players because defences are so well drilled and strong.
"He has good footwork while having the same kind of destructive power as the likes of Aleki Lutui and Dale Rasmussen."
Tu'ipulotu added: "I'm very pleased with the move to Worcester and the chance to play the brand of rugby that Warriors will look to adopt in the Aviva Premiership.
"It's amazing that the team has won promotion and I really enjoyed being at the stadium on the day of the final to watch it all happen.
"The team deserves great praise for the way they have performed all season and I look forward to joining up with the squad this summer as we look to make an impact in the top-flight.
"It was a great honour to play for Plymouth, where I made many friends, and now I hope to have the same success at Warriors."