Diagne also grabbed 10 rebounds. Shivaughn Wiggins added 13 points and Colton Ray-St Cyr chipped in 10 as Coastal Carolina (3-2) beat Charleston on its home floor for the first time since the 1976-77 season.
The score was tied eight times and there were 13 lead changes. Coastal Carolina took the final lead with 2:29 remaining when Jaylen Shaw drove for a layup as the Chanticleers scored eight unanswered points to go ahead 63-55 with 52 seconds left.
The Chanticleers made 26 of 47 (55.3%) from the floor while limiting Charleston to 20 of 59 (33.9% shooting). Coastal Carolina also scored 34 points in the paint, while holding the Cougars to just eight.
Cameron Johnson had a career-high 20 points to lead Charleston (2-2).