The 6-foot-9, 245-pound Oriakhi will provide an instant inside presence to a Missouri team that had only one player taller than 6-8 last season. Oriakhi blocked 166 shots in 109 games at UConn.
"Missouri needs a center, and I'm going to be the center," he told the Kansas City Star. "It's a perfect match."
He has one year of eligibility and can play immediately because UConn is banned from next season's NCAA tournament. UConn doesn't qualify because of several years of below-standard Academic Progress Rate scores. The university had requested a waiver, arguing that recently instituted reforms have led to improved scores over the past two seasons, but the NCAA turned down that request earlier this month.
Oriakhi averaged 7.2 points and 6.8 rebounds per game in three seasons at UConn, and was part of the team that won the 2011 national championship.
He chose Mizzou over Kentucky, Xavier, Duke and North Carolina.
"This is where I wanted to go from the beginning. It was just a matter of me visiting," Oriakhi told the Star.
Oriakhi and Missouri point guard Phil Pressey played together as youths for the Boston Amateur Basketball Club.
"We went right to the gym (Thursday night)," Oriakhi told the Star. "A lot of these guys, from what I've seen, they're all workhorses, and they sleep in the gym. I want to be a part of a team like that."
Missouri coach Frank Haith, who will lead the Tigers into their first season in the SEC, welcomed the new addition.
"We're very excited to add a talented and proven player like Alex to our program," Haith said in a statement. "Addressing our front-court depth has been a major emphasis of ours for this next year, and when you add Alex to a group of newcomers including Stefan Jankovic, Ryan Rosburg and Tony Criswell, we are definitely heading the right direction.
"Alex is a very hard worker, he's somebody who we expect to fit into our program's culture right away. He will do whatever he's asked to help the team, and he can impact a game any number of ways, whether it's scoring, rebounding or defending."