Trevor Cooney stole an inbounds pass in the closing seconds but missed a 3-pointer from the corner that would have given the Orange the lead.
Blossomgame led the Tigers (9-6, 2-1 ACC) with 20 points. Nnokomo equaled his career high with 19 and snared 10 rebounds before fouling out in the extra period.
Syracuse has not started a season 0-3 in league play since 1996-97 as a member of the Big East Conference.
It was the final game as interim coach for Syracuse's Mike Hopkins. Jim Boeheim returns Wednesday after serving a nine-game suspension imposed by the NCAA.
Blossomgame's lay-in gave the Tigers a 65-63 lead a minute into the overtime, but Richardson-s 3-pointer gave the Orange its only lead in the extra session at 66-65 with 3:01 to go.
A three-point play by Nnoko gave Clemson a 70-66 lead, and the Tigers survived the tense final seconds.
A 3-pointer by Tyler Lydon brought Syracuse to 74-73 with 12 seconds to go. Cooney then stole the inbounds pass, lost it briefly with a bad pass before Gbinije corraled it to set up Cooney's potential game-winning 3.
Gabe DeVoe's 3-pointer from the corner with 11 seconds left in regulation forced the overtime after Richardson appeared to have lifted the Orange to a thrilling come-from-behind win.
Richardson scored the last six Syracuse points in regulation, including a desperation 3-pointer over a double team in the corner with no time left on the shot clock to give the Orange a 61-58 lead with 18 seconds to go, setting up DeVoe's heroics.
Richardson missed the second of two free throws with 18 seconds left that would have given Syracuse a four-point lead and rendered DeVoe's shot moot.
The teams traded buckets for much of the second half. Gbinije's 3-pointer, his third of the game on nine attempts, pulled Syracuse to 50-48 with 9:02 to go. Another 3-pointer by Gbinije with 5:50 left gave Syracuse its first lead, 51-50, since 7-2 early in the first half.
The teams then went back and forth. Richardson's two free throws gave Syracuse a 57-56 with 1:57 remaining.
Boeheim, who was suspended after a long NCAA investigation into the athletic department that uncovered academic violations in men's basketball, returns to the sidelines Saturday night when the Orange host No. 6 North Carolina. Hopkins compiled a 4-5 record.
Clemson: Clemson had not won on the road before Tuesday, going 0-3. ... Blossomgame ranks in the top 20 in the ACC in scoring and rebounding. ...The Tigers were making 35 percent of their 3-point attempts and hitting 8.1 per game from beyond the arc. They finished 8 of 17 against Syracuse. ... Clemson is third in the ACC in scoring defense and leads the conference in blocked shots.
Syracuse: Freshman guard Franklin Howard missed his second consecutive game due to an undisclosed illness. ... Gbinije was hoping to rebound from a 3-for-14, 0-for-7 from the 3 performance at Miami. He finished 7 of 19 and 4 of 13 on 3s. Prior to Tuesday, Gbinije was just 1-of-11 shooting from the 3 and 9-of-19 from the foul line in the previous two games, losses at Pitt and Miami. .Gbinije has scored in double digits every game.
Syracuse hosts North Carolina Saturday night.
Clemson is home Sunday against Louisville.
AP College Basketball Website: www.collegebasketball.ap.org