During his Monday show, Hannity, who said he utilizes eight separate attorneys, said the media was going "nuts" about the story because they think Cohen was involved in "a big settlement case for Hannity".
Prosecutors with the United States attorney's office in Manhattan said they have a "filter team" of lawyers separate from those involved in the investigation in place to review the documents for any communications between Cohen and his clients.
A gasp was heard in the courtroom when a Cohen lawyer disclosed the name of the third client: Sean Hannity.
Hannity has been a champion of Trump's and Cohen's on his show and a critic of the Federal Bureau of Investigation and Justice Department; former House Speaker Newt Gingrich said on Hannity's show last week that the Federal Bureau of Investigation raid on Cohen was like the abuses of the "Gestapo".More news: March Retail Sales Rose 4.5% YOY
It was not immediately clear what legal work Cohen provided for Hannity. He later added: I "may have" handed Cohen "ten bucks" and asked for attorney-client privilege.
"I never retained him in the traditional sense as retaining a lawyer, I never received an invoice from Michael, I never paid legal fees to Michael, but I have occasionally had brief discussions with him about legal questions about which I wanted his input and perspective".
"Michael Cohen has never represented me in any matter", Hannity said in an e-mailed statement provided to Reuters.
Late Sunday, lawyers for Trump asked for copies of the seized material to be turned over so the President could review them for confidential information.More news: Thousands of protesters take to the streets in Armenian capital
Cohen is under criminal investigation, prosecutors confirmed last Friday.
Earlier in the day, Cohen's attorneys argued that the third client's name should remain anonymous.
The search warrant authorizing the raid indicated prosecutors were looking into potential violations of bank fraud, wire fraud, and campaign finance violations, sources told CNN. The attorneys said in the filing that Cohen represented three clients in the past year: Trump; Elliot Broidy, the Republican fundraiser for whom Cohen helped facilitate a $1.6 million payment to a Playboy playmate; and a third person, who was revealed as Hannity.
Cohen has acknowledged paying pornographic actress Stormy Daniels $130,000 for what her lawyer said was silence about her alleged liaison with Trump shortly before the 2016 election.More news: Bella Hadid and The Weeknd kissing at Coachella
Trump denies any sexual relationship with Daniels.