Stormy Daniels, 38, caused a huge scrum as she arrived to see the president's personal lawyer argue which of his files the Federal Bureau of Investigation should be allowed to pass to criminal prosecutors.
As the hearing got under way, Cohen sat by his lawyers, looking tense and clasping his hands on a table before him.
The Justice Department has said last week's searches stemmed from "a months-long investigation" and seek evidence of crimes by Cohen, "many of which have nothing to do with his work as an attorney".
Cohen's attorneys said in a filing that Cohen had represented three clients in the past year, including Trump and Elliott Broidy, a Republican fundraiser.
Investigators are looking for the possible secrete deals that Cohen may have made to protect candidate Trump, one of them with adult film star Stormy Daniels. But Judge Wood said she would still need the names of those other clients, and rejected his efforts to mask the identity of Hannity, a client Cohen had said wanted to avoid publicity.
Michael Cohen is under criminal investigation for personal business dealings and was ordered to appear in federal court Monday in NY to help answer questions about his law practice.
"Anyone that had any contact with this man in the last 20 years should be very concerned about what secrets of theirs are within these documents", he said.
Cohen, who the judge had ordered to appear in court on Monday, has continued to make headlines.
An email sent to Fox News seeking comment from Hannity was not immediately returned.
He assumed those discussions were covered by attorney-client privilege, he said on the show, which Fox says reaches more than 13 million listeners. In a tweet, Hannity said it was "almost exclusively about real estate".
Legal advice can be considered privileged even if given by a lawyer for free. The federal prosecutors in Manhattan argued that granting Cohen's lawyers that authority would be unprecedented, and that the use of a special government team would be more appropriate than appointing a special master. He never mentioned his association with Cohen during the broadcast.
In their letter to US District Judge Kimba Wood, Cohen's attorneys, Todd Harrison and Stephen Ryan, wrote that the third client did not allow them to disclose that they had used Cohen's services.
Prosecutors have asked that the documents be reviewed for attorney-client privilege by a "filter team" of lawyers within their own office, who would be walled off from the main prosecution team. According to Stormy's attorney, she will be present at Trump attorney hearing.
Daniels, in contrast, stepped up to the bank of microphones set up on the sidewalk, telling reporters that Cohen had thought he was above the law.
"My attorney and I are committed to making sure that everyone finds out the truth and the facts of what happened", she added.