Lowry twisted his right ankle after landing on Thunder forward-centre Serge Ibaka's foot while going for a rebound in the second quarter.
Lowry grimaced as he pounded the floor and had to keep his weight off the foot as he went to the locker-room.
He did not return for the second half, and Toronto went on to lose 108-88.
A Raptors team spokesman said Lowry was wearing a walking boot as a precaution, and that he would receive further treatment Wednesday. There is no timetable for his return.
The 26-year-old is playing in his first season with the Raptors after being acquired in the off-season from the Houston Rockets.
Lowry entered Toronto's fourth game of the season averaging 23.7 points per game, 7.3 rebounds per game and seven assists per game.