O'Neal came off the bench and finished with five points and five rebounds against the Indiana Pacers, who won 96-94.
"It's good to be out there with the guys, but obviously there's a lot of rust," O'Neal said. "The rust will wear off and I'll get my rhythm back."
O'Neal, a key component to the Heat's NBA title run last season, had surgery on Nov. 19. The 7-foot-1, 325-pound (146-kilogram) center had played in only four games before he was injured, averaging 14 points and 7.5 rebounds.
The Heat have struggled without O'Neal, their record falling to 19-23, reports AP.
Despite the loss, Dwyane Wade was happy to have O'Neal back in the lineup.
"We're a much more powerful team with him," Wade said.
Putin said that NATO increased its military personnel by 10,000 people in the areas where NATO troops should not even be in accordance with key documents
The choice of the city of Helsinki is not incidental as the capital of Finland had hosted US-Soviet negotiations on the limitation of nuclear stockpiles in 1969