Scott Green was dressed in surgical scrubs in an operating theatre when he appeared at his virtual trial on Thursday, the Sacramento Bee reported.
When questioned by the judge, Mr Green said he was happy to go ahead, and that he had "another surgeon right here who's doing the surgery with me".
The judge said that would not be "appropriate" and postponed the trial.
The Medical Board of California has now said in a statement that it would look into the incident, adding that it "expects physicians to follow the standard of care when treating their patients".
Before the Sacramento Superior Court hearing, which was livestreamed on YouTube, a court clerk asked the plastic surgeon: "Hello, Mr Green? Hi. Are you available for trial? It kind of looks like you're in an operating room."
Green responded: "I am, sir. Yes, I'm in an operating room right now. Yes, I'm available for trial. Go right ahead."
The clerk told Mr Green that the hearing was being livestreamed online, because traffic hearings are required by law to be open to the public. At the same time, an officer summoned to appear in court raised her eyebrows.
While waiting for the judge, Court Commissioner Gary Link, to enter the Zoom, Mr Green appeared to continue operating on the patient.
Once Mr Link had joined, he told the hearing: "So unless I'm mistaken, I'm seeing a defendant that's in the middle of an operating room appearing to be actively engaged in providing services to a patient. Is that correct, Mr Green? Or should I say Dr Green?"
After the surgeon confirmed he was in the middle of performing surgery, and that he would be happy to continue, Mr Link said: "I do not feel comfortable for the welfare of a patient if you're in the process of operating that I would put on a trial, notwithstanding the fact the officer is here today."
Mr Green then insisted he was able to go ahead, adding: "I have another surgeon right here who's doing the surgery with me, so I can stand here and allow them to do the surgery also."
Mr Link replied: "I don't think so, I don't think that's appropriate. I'm going to come up with a different date - when you're not actively involved or participating and attending to the needs of a patient."
BBC News has contacted Mr Green's office for comment.
The surgeon reportedly told NBC News: "That's not accurate and I have nothing to say. Thank you."
This isn't the first Zoom court mishap to go viral.
Earlier this month, a lawyer was unable to remove a cat filter from his screen, before telling the judge he was happy to go ahead anyway: "I'm here live, I'm not a cat."
The Duke of Sussex has drawn parallels between the treatment of his mother and wife, in teaser clips of a much-anticipated Oprah Winfrey TV special.
In two 30-second clips released by CBS, Harry says he feared history was "repeating itself" before he and Meghan decided to step back as senior royals.
Winfrey is seen asking Meghan if there had been a "breaking point" and if she was "silent or silenced", but the duchess does not speak in either clip.
The US interview airs on 7 March.
It is unclear when the programme, Oprah With Meghan And Harry: A CBS Primetime Special, will be shown in the UK.
In the full programme Meghan will talk about marriage, motherhood, life as a royal and how she is handling "intense public pressure", CBS said.
Prince Harry has previously said he stepped back from royal duties in order to protect himself and his family from the "toxic" environment created in the UK by the press.
Harry's late mother Diana, Princess of Wales, relinquished the Her Royal Highness title at the time of her divorce from the Prince of Wales in August 1996.
She died the following year after a car crash in Paris. The driver had been drink-driving and the car was being followed by paparazzi on motorbikes when the accident happened.
In the clips from the upcoming TV special, an image of a young Prince Harry with Diana is shown as the duke says: "I can't begin to imagine what it must have been like for her going through this process by herself all those years ago, because it has been unbelievably tough for the two of us - but at least we had each other."
Harry also tells Winfrey: "My biggest concern was history repeating itself.
"For me, I'm just really relieved and happy to be sitting here, talking to you with my wife by my side."
These first insights into the much-anticipated Oprah interview are designed to draw us in with their tight editing and dramatic music.
They are a flavour of what's to come.
In the minute of footage, Meghan doesn't say a word. We'll have to wait for her answers.
But the questions that Oprah puts to her hint strongly at upset and frustration. The language is of being silenced and of surviving something.
The talk from Harry is of protecting his wife and being able to escape from the pressure and strain they felt.
In Oprah, the couple chose a friend to interview them whose style isn't aggressive.
She is an expert at getting interviewees to open up and she will have encouraged them to reveal what went wrong behind the palace walls.
It is that which will worry the Royal Family and palace officials.
How critical have Harry and Meghan been? We will find out when the full interview is broadcast next weekend.
- The political organization founded by NBA superstar LeBron James and a host of other Black athletes and artists will kick off its post-2020 work with a focus