Aston Villa boss Paul Lambert refused to shake the Portuguese's hand as he prepared to head down the tunnel before the end of his side's 3-0 defeat by the Blues at Stamford Bridge on September 27, and his assistant Keane's reaction was even more withering.
Asked about the incident as he launched his new autobiography, The Second Half, in Dublin on Thursday afternoon, Keane said: "It's disgraceful.
"I've seen him doing it to other managers, it is a disgrace
The game is still going on
You wouldn't do that on a Sunday morning, you would get knocked out."
But while Mourinho found himself in the firing line, it was Keane's former Manchester United manager Sir Alex Ferguson upon whom the spotlight fell as Keane discussed the falling-out between the pair as his time at Old Trafford drew to a close in 2005.
The relationship between the two men deteriorated beyond the point of no return with the then United captain's infamous MUTV interview and his reference to Ferguson's involvement with the syndicate which owned racehorse Rock of Gibraltar helping to bring matters to a head.
Keane, who insisted he only ever had " five, six" one-to-one talks with the Scot during his 12-and-a-half years at United, was nevertheless not afraid to have his say, but admitted other managers were intimidated by Ferguson.
He said: "I think a lot of managers would probably be intimidated by him, probably bow to him
I think a lot of managers are heavily influenced by him, of course.
"I think (Everton boss Roberto) Martinez reckons he was misquoted a few years ago (saying) that Ferguson had his disciples
He obviously does.
"When a manager takes players away from being on loan - I think it was Preston when Ferguson was manager - when his son (Darren) got the sack, and, all of a sudden, the players are coming away on loan."
Ferguson used his own autobiography, published last year, to settle his own scores with Keane and David Beckham among those to come in for criticism, a move described as "ridiculous" by the Irishman.
The Scot suggested at one point that the hardest part of the midfield enforcer was his tongue, a barb which produced a cutting response.
A smiling Keane said: "Well, what do you think? I kick pretty hard.
"I think it was a cheap dig
He was never critical when we were winning trophies and he was getting his new contracts, getting this after him, Sir this.
"He was not pulling me or other players, saying, 'Listen, you need to relax a bit'
That was the game and I appreciate the game
The game finished, but it was all the carry on afterwards."
Source : PA