Andre Iguodala had a chance to tie the game for the Nuggets with 3.4 seconds to play, but he missed the third of his three free throw attempts to leave Golden State with the victory.
Iguodala then hit a 3-pointer as the buzzer was sounding, but a look at television replays by the officials determined he got off the shot a fraction of a second after time had expired.
The Warriors rallied from a nine-point deficit late in the third period to win their second in a row and move three games above the breakeven mark.
David Lee led Golden State with 31 points, hitting 13-of-15 from the field. Klay Thompson added 21 and Jack had 18, including a layup that gave Golden State a 106-103 lead.
Iguodala scored 22 points and Danilo Gallinari had 20 for the Nuggets, who have dropped back-to-back games.