McNamara's jumper gave Syracuse the lead for good with 4:41 left. His second three-pointer of the extra session put the Orangeman ahead, 88-80, with 2:41 to go.
Mike Sweetney converted four consecutive free throws to pull the Hoyas within, 88-84, with 1:58 left, before Craig Forth dunked for Syracuse. McNamara put in two from the line and Kueth Duany added another free throw for the final margin.
Syracuse took its first lead of the game, 62-60, on a steal and jumper by Anthony with 6:18 left in the second half.
Courtland Freeman gave Georgetown a 74-71 lead with a free throw with 67 seconds left in the half, but freshman Billy Edelin scored five straight points to give Syracuse a 76-74 advantage with 47 seconds remaining in regulation.
Anthony missed two shots from the line that would have given the Orangemen a four-point advantage, but the Hoyas could not capitalize and McNamara pushed Syracuse's lead to 77-74 with a free throw with 11 seconds left.
However, Gerald Riley drained a 3-pointer from the top of the key off a broken play with three seconds to go in regulation to knot the game at 77-77. Edelin attempted a half-court heave just before the buzzer but it hit the backboard.
Warrick finished with 14 points and 18 rebounds for Syracuse (21-4, 11-3 Big East West), which won its fifth straight game and remains in control of its own destiny. The Orangemen, who lead the West division, need just two more wins to claim at least a share of the division title.
Sweetney scored 27 of his 31 points after the first half, grabbed 19 rebounds, dished out seven assists and blocked seven shots. Georgetown (13-12, 5-9) fell to 1-7 in overtime over the past two years, including three losses this season.