Dixon was suspended for a violation of team rules before the season and has not played for the 16th-ranked Tigers this season.
Though no charges have been filed, Dixon was twice accused of sexual assault during his time at Missouri, according to police incident reports.
A female student accused Dixon of sexual assault in a weekend Twitter exchange with former Missouri guard Kim English, who is now with the Detroit Pistons. The woman also filed a police report in August, copies of which were publicly released this week, but Boone County prosecutors decided Nov. 16 not to file charges.
Dixon, the one-time prep star from suburban Kansas City, was briefly suspended for violating team rules in December 2010 by former Missouri coach Mike Anderson, who is now at Arkansas. That suspension involved a woman who worked in the Missouri athletics department. She later decided not to press charges
Dixon didn't address the allegations in the university's announcement.
"It's been a challenging few months and while I appreciate the support of many in the Mizzou community, including my coaches and teammates, it's in the best interest of me, my family and the University of Missouri for me to finish my career elsewhere," Dixon said in the statement.
English was among the most vocal of Dixon's supporters, defending his former teammate's "poise, class and professionalism" on Twitter while also praising Missouri coach Frank Haith and chancellor Brady Deaton. But he called a university disciplinary board apparently investigating Dixon "a joke" and said his alma mater "should be ashamed!" Those criticisms were later deleted -- as was the 19-year-old sophomore's online accusation that prompted English's comments.
Dixon posted his own defense that "I've done nothing wrong!" on Twitter a week ago but later had it removed.
Dixon, who won the Show-Me Basketball award in 2009 as the state's top high school player, did not respond to several messages left on his cellphone the past several days seeking comment. The Columbia Missourian reported Thursday that Dixon sent a friend a series of text messages confirming his departure, alluding to the earlier assault complaint and insisting that "I have never harmed anyone."
Dixon averaged 13.5 points last season and was voted national sixth man of the year by some media outlets. He was expected to start this year.
Haith had declined to discuss the reasons for Dixon's suspension, which he said did not involve NCAA matters or legal issues -- a characterization subject to interpretation given that the case remained under review by local prosecutors until two weeks ago. Most recently, Haith said he would not talk about the "rumors and allegations" involving Dixon.
Dixon traveled with the team this month to the Bahamas for the Battle 4 Atlantis tournament, where Haith spoke as if he expected Dixon to return from his suspension.
"It's all about teaching," Haith said when asked why Dixon traveled with the team. "If I leave him back home, what does that do? I want him to feel (the pain of not playing)."
Missouri, led by preseason SEC player of the year Phil Pressey at point guard, has started both Pepperdine transfer Keion Bell (8.7 points per game) and freshman Negus Webster-Chan (6.8) in Dixon's place at shooting guard.
The Tigers will get more relief in the backcourt when Oregon transfer Jabari Brown becomes eligible after the semester ends Dec. 14.
"We're not going to be very fluid on offense right now," Haith said in the Bahamas, where the Tigers beat Stanford and VCU but lost to then-No. 2 Louisville. "We don't have all of our weapons. Mike Dixon and Jabari Brown are offensive weapons."
Information from The Associated Press was used in this report.