A Manhattan judge gushed about being a longtime WFAN fan — before slapping Craig Carton with a 3½-year prison sentence on Friday.

“Colleen from New York. First time, long time,” federal Judge Colleen McMahon greeted the former radio host midway through the two-hour hearing.

The jurist said she’d listen to Carton’s hit show “Boomer and Carton” every day on her drive to the courthouse in Lower Manhattan.

“You could be fun to listen to,” she told the 50-year-old, who resigned from the show a week after he was arrested for running a Ponzi scheme in order to repay his gambling debts.

McMahon added, “I also knew you could be a jerk … things could get a little raunchy.”

She told Carton that she appreciated how he candidly spoke about living with Tourette syndrome on the show.

“You had put your celebrity to good use and a lot of people benefited and I like you for that,” McMahon said.

She said after learning of his arrest, she’d hoped his fraud didn’t involve his Tourette charity Tic Toc Stop Foundation.

“I can’t tell you how relieved I was,” she told him about finding out the nonprofit wasn’t involved.

McMahon’s penchant for “Boomer and Carton” was first revealed ahead of jury selection last October.

“I have no idea how many WFAN listeners we will have,” she told lawyers on the case. “I, by the way, am a WFAN listener. I listened to Mr. Carton for years.”

Carton was replaced by Gregg Giannotti, who now appears alongside NFL quarterback Boomer Esaison on their “Boomer and Gio” show.