The former Baltimore Ravens offensive tackle tweeted that he's "extremely happy and excited to be a Titan (and) can't wait to do big things!!!"
Oher also tweeted, "Wanna thank the Ravens organization and their great fans!"
The deal is for four years and $20 million, a league source told ESPN NFL Insider Adam Schefter. It includes $9.5 million in guaranteed money.
"Michael is a big, strong, durable player," Titans general manager Ruston Webster said in a statement. "Like we have said with a number of players we added this week, he has versatility with experience playing both left and right tackle during his NFL career. We are excited to have Michael as part of the Titans family."
Even though Oher's life story inspired the movie "The Blind Side," he has played left and right tackle throughout his career, stepping into the spot the Ravens needed him the most.
The Ravens counted on Oher for his toughness and durability, and they considered him a throwback type of player. He has never missed a game in his career and became the first Ravens rookie offensive lineman since Jonathan Ogden in 1996 to start all 16 games.
But Oher hasn't lived up to the expectations of being the 23rd overall pick from four years ago. He never became a top-notch left tackle and has ended up being an average right tackle. Penalties (24 false starts in his career) and pass protection have long been trouble areas for Oher.
Oher, 27, should fill Tennessee's vacancy at right tackle created by the Titans' decision to waive David Stewart on Wednesday. Stewart had been Tennessee's starting right tackle since 2006.
ESPN.com Ravens reporter Jamison Hensley and The Associated Press contributed to this report.