Tyrell Nelson had 15 points and nine rebounds for Gardner-Webb. Adonis Burbage scored 13 and Tyler Strange had a career-high 14 assists.
A 3-pointer by Longwood's Leron Fisher tied it a 56 with 9:35 left, but Gardner-Webb (13-7, 5-2 Big South) responded with a 10-0 run, the last four by Hill, over the next five-plus minutes.
After a layup from Darrion Allen and another Fisher 3 pulled Longwood (6-15, 2-6) within 66-61 with three minutes to go, Hill scored six straight for Gardner-Webb to start a 13-3 run which made it 79-64 with 13 seconds remaining.
Fisher made a career-high five 3-pointers and led Longwood with 25 points. Shaquille Johnson added 19 and seven rebounds.