Pinson started 31 games as a sophomore last season, averaging 11.1 points while shooting 40% from the field. Smith will be a fifth-year senior after the 6-foot-10 senior averaged 5.1 points and 4.9 rebounds.
Tilmon also will be a senior and has averaged 8.9 points and 4.9 boards over 81 games in his career. The 6-foot-10 Tilmon was a top-50 recruit in 2017 but has struggled to stay out of foul trouble throughout his career.
"Coming back for my senior year, I want to finish school, finish strong, get my degree," Tilmon said in a video on social media. "We got a good group of guys coming in, and we've got unfinished business, M-I-Z."
Coach Cuonzo Martin's roster will have 11 players who are juniors or seniors, the most in the Southeastern Conference and third most among all Power 5 programs. They will have just one true freshman on the roster this season in 7-foot-2 center Jordan Wilmore.
Missouri went 15-16 last season, its second consecutive losing season among Martin's three seasons in Columbia.
Information from The Associated Press was used in this report.