Prosecutors say Ronagal Lamar Outlaw of Starkville entered the plea Tuesday in Lowndes County Circuit Court.
Outlaw is scheduled to be sentenced Friday and could get up to 40 years in prison.
Outlaw pleaded guilty to fatally shooting 23-year-old Trumaine Macon at the CrossRoads Lounge in west Lowndes County last February.
Outlaw, who was a Starkville High School student at the time of the murder, shot at Macon multiple times after the two got into an argument. Macon died at a local hospital.