Senior Nick Cook's eight points led JSU, which dropped to 4-8 on the season. Junior Darion Rackley added seven points and a team-high five rebounds
Four players scored in double figures to pace Dartmouth, which is now 4-4 after breaking a three-game losing streak.
The Gamecocks shot just 30.4 percent from the field and were outrebounded 46-23.
Darmoth's Alex Mitola scored 16 points behind a 4-of-7 night from behind the 3-point line, while John Golden added 14 points. Tyler Melville and Brandon McDonnell each finished with 12 points.
The Gamecocks struggled from the field in the first half, shooting just 6-of-26 (23.1 percent) while watching the Big Green knock down 6-of-13 from 3-point range while shooting 48 percent (12-of-25) from the field.
Freshman Undra Mitchem knocked down a trey to tie the game 10-10 before Dartmouth used a 10-0 run to take a 20-10 lead with 10:14 to play. Cook then ended a four-minute scoring drought for JSU with a layup underneath to break up the Big Green run.
Mitola then hit his third 3-pointer of the half with 5:09 to play to give Dartmouth a 31-15 lead. The Big Green closed the half hitting six straight free throws while building a 37-17 lead at the break while holding the Gamecocks scoreless for the final 2:24 of the half.
The Big Green continued its hot shooting night in the second half, converting their first nine shots of the final period while building a 57-29 lead with 12:31 to play. For the half, Dartmouth shot 60.9 percent (14-of-23) from the field and converted 10-of-14 (71.4 percent) free throw attempts.
The Gamecocks continued to struggle from the field in the second half, hitting just 11-of-30 (36.7 percent) shots from the field while finishing 3-of-6 from the free throw line. For the game, the Gamecocks were 7-of-15 (46.7 percent) from the free throw line.
JSU managed to cut the lead to 63-41 with seven minutes to play with the help of a 12-6 run. Juniors Teraes Clemmons and Grant White each knocked down a 3-point shot before Avery Moore knocked down a jumper. White then hit another jump shot before junior D.J. Felder found sophomore Mike Louder underneath for a dunk to cut the lead to 22 with 7:22 remaining.
The Big Green then outscored the Gamecocks 13-5 to close the game while converting on 7-of-8 free throw attempts to help put the game away for the 76-46 victory.
The Gamecocks will return home Tuesday to face Central Michiganat 7:45 p.m.