Clemson announced on Friday that 23 football players have tested positive for coronavirus since returning to campus this month.
Schools spokesman Jeff Kallin said that in all 28 people were found with COVID-19 since testing began for athletes and other personnel on June 8.
Two football staffers and three athletes from other sports also tested positive.
Those known to have close contact with those that tested positive have been asked to quarantine for at least 10 days. The athletic department said most of the total cases have been asymptomatic and no one has been hospitalised.
Clemson is the latest program to see positive test results from athletes returning to school. Texas, Houston and SMU have all had football players test positive since voluntary workouts resumed.