TMZ Sports obtained footage and had the following information on the incident:
It all went down after Okafor and the 76ers lost to the Boston Celtics -- Jahlil and some friends went out on the town ... and ended up in an altercation in front of Storyville Boston nightclub.
We spoke with a rep for Jahlil who tells us ... Okafor says he was being heckled from the moment he left the club and felt threatened because people swarmed him on the street.
He says he was with a teammate -- who he wouldn't name -- and says someone got physical with the teammate ... so Jahlil did what he felt he needed to do to protect himself and his friend.
According to TMZ, no arrests were made and everyone involved fled the scene.
Okafor was the third overall pick in this year's draft, so footage of him punching a man in the face is not something the front office wants to see.
Earlier in the night, Philadelphia's horrible start to the season continued, losing 84-80 to the Celtics, with Okafor recording 19-points and nine rebounds.
The Sixers have endured a woeful 0-16 start to the season to become the only team in NBA history to record such poor number two seasons in a row.
The 76ers released a report in the aftermath of the Okafor street-fight.
"We are aware of the report and we are currently working to gather additional information," it said.
"Until that time, we will have no further comment."