Philadelphia rookie Marreese Speights scored 10 of his 12 points in the fourth quarter, and Louis Williams chipped in 10 points for the 76ers (2-1).
Jason Kapono led Toronto with 14 and Will Solomon had 12. Andrea Bargnani and Anthony Parker also scored in double figures, netting 10 points each, for the Raptors (2-1).
Elton Brand had 10 points and nine rebounds in 29 minutes for Philadelphia.
Toronto's Chris Bosh was held to just four points in 23 minutes, going 1-for-5 from the floor. Jermaine O'Neal had nine points in 25 minutes for the Raptors, who lost for the first time in 12 preseason games at Air Canada Centre.
Will Solomon fouled Williams with 0.1 seconds remaining in the third on a 3-point attempt. Williams made two of three to tie it at 60.
Kapono tied it at 77 on a jumper with 3:48 to play, but the 76ers scored eight of the final 10 points, including two dunks by Speights and a game-sealing dunk from Igoudala with 12.9 seconds remaining.
Toronto led 41-39 at the half.
Toronto was without F Joey Graham (hamstring), C Nathan Jawai (heart) and C Jamal Sampson (wrist). Philadelphia did not have forward Jason Smith (knee). Former Raptor Donyell Marshall also didn't play for the 76ers, and G Roko Ukic did not play for Toronto. ... Actor Ving Rhames attended the game.