Mourinho cupped his hand to his ear after United’s 2-1 victory over Juventus in the Champions League in Turin on Wednesday night.
The Red Devils chief was responding to fans who had hurled abuse at him throughout the game.
And Ancelotti copied his provocative celebration when he was asked for his thoughts on Mourinho in a press conference ahead of his side’s Serie A clash with Genoa this weekend.
“Sorry, I did not hear you,” he responded, before mimicking Mourinho’s hand action.
“Mourinho? His reaction is understandable because it wasn’t a vulgar thing to do, it was more ironic.
“When you are being insulted for 90 minutes it can happen.”
Mourinho’s United came from a goal down to secure an important three points at the Juventus Stadium.
They had been under intense pressure after Cristiano Ronaldo’s 65th-minute opener.
Juan Mata curled home a free-kick to equalise with just four minutes left on the clock before Leonardo Bonucci bundled Ashley Young’s set-piece into his own net three minutes later.
And Mourinho insisted his celebration was not meant to upset the Juve fans.
“That sign that I made is actually not an offence,” the former Inter Milan boss said.
“I just wanted to hear if they’d [the fans] make comments again or not.
“Obviously when I work for a club like Manchester United, I need to forget my past, especially in the 90 minutes.
“It’s not that during the 90 minutes I keep thinking I was coach of Inter or Real Madrid or Chelsea.
“In those 90 minutes I represent Manchester United.”