Arkansas shot just 27 percent in the first half and trailed 29-23 at the break. USC stretched the lead to 40-27 and had a 44-35 advantage with 10:52 to play on a Michael Boynton jumper.
Dean, who was two of four for a team-high six points in the first half, took his first shot of the second half at the 10:42 mark and nailed a three-pointer to get the Hogs within 44-35. He scored on two layups and a dunk over the next two minutes to cut the deficit to 47-44.
Marius Petravicius made two free throws to give the Gamecocks, who have lost only to Duke, UCLA, Kentucky, Florida and Georgetown this season, a 58-53 lead with 4:26 to play.
Teddy Gipson made two free throws and Dean hit a three-pointer to tie the game with three minutes remaining, and Carl Baker's free throws tied the game at 60-60 with 1:28 to go.
Jamel Bradley, who led USC with 16 points, converted a layup to give USC the lead and Arkansas turned the ball over. The Razorbacks got it back on a turnover but lost the ball again. With seven seconds remaining, Petravicius missed a free throw, but Arkansas missed two shots to win or force overtime, the last coming with 0.3 seconds remaining.
Arkansas forced 20 turnovers and held USC to 46 percent shooting, but the Hogs turned the ball over 17 times and even with a hot-shooting second half (.524) still shot just 39.5 percent for the game.
Dean was seven of 10 overall and four of six on three-pointers for a game-high 18 points. Jannero Pargo made five of 12 shots and had 14 points. Gipson and Baker added six points each.
Rolando Howell had 12 points for the Gamecocks while Petravicius and Aaron Lucas had 10 each.
Arkansas plays host to Ole Miss Saturday at 5 p.m. in a game televised by SEC-TV, which will be carried in Northwest Arkansas on Fox Sports Southwest.