Celebrity chef George Calombaris will appeal against a Sydney magistrate's decision to record a conviction over his assault of a teenager at the A-League grand final in May.

Calombaris, who is best known for his role on Channel 10's MasterChef, has been fined $1,000 for punching a 19-year-old Sydney FC fan in the stomach at the Sydney Football Stadium.

The 39-year-old pleaded guilty to common assault after video emerged of him confronting the fan, then being ushered away by police.

In video of the incident, Calombaris shakes his Melbourne Victory scarf at the victim, who was yelling abuse.

Calombaris then approached the man and shoved him in the chest.

In handing down the sentence in the Downing Centre Local Court on Friday, Magistrate Peter Miszalski said "to deliberately punch someone, someone you don't know, it calls for some element of deterrence".

"It's a very public display of aggression," he said.

Calombaris' lawyer told the court the chef reacted to abusive taunts from the crowd, particularly about his mother, and was deeply sorry for his actions.

However, Mr Miszalski said it was Calombaris who approached the victim and not the other way around.

"He's actually made his way into the crowd," he said.

"You don't get sucked into the drama. Once you do that, you're gone."

Celebrity chef George Calombaris admitted to assaulting a teenager after the A-League grand final earlier this year. ( AAP: Joel Carrett )

The court heard there had been "profound" consequences for Calombaris as a result of media coverage of the incident, including the loss of a $300,000 ambassadorship.

Mr Miszalski said: "I'm sure those people probably labelled him a thug."

The magistrate said he was a fan of the TV show MasterChef "a long time ago" and to see someone like Calombaris come before the court was a "tragedy".

Calombaris's lawyer argued a conviction should not be recorded against his client given his remorse and the negative publicity he had received as a result of the case.

But the magistrate disagreed and recorded a conviction and fined the chef and restaurant owner $1,000.

The appeal against the recording of a conviction will be heard in January.

The owner of Melbourne restaurants The Press Club, Gazi and Hellenic Republic earlier stood down as Melbourne Victory's number one ticket holder.