The 20th-ranked Tigers (30-4) advance to the NCAA tournament after going undefeated in the regular conference season and winning the conference crown for the third consecutive season.
Chris scored seven points in overtime and Joe Jackson scored 22 for Memphis, which outscored Southern Mississippi 19-7 in the second overtime period.
Daveon Boardingham led Southern Mississippi (25-9) with 19 points and eight rebounds. Dwayne Davis chipped in 16.
Southern Mississippi joined the ranks of the NCAA bubble teams.