The Republic of Ireland assistant manager, 43, denied the public order offence after driver Fateh Kerar, 44, had told him to “cheer up” and smile.
The former Manchester United captain gave evidence from the witness box himself and after a half-day trial at Manchester Magistrates’ Court he was cleared of the offence.
District Judge Duncan Birrell said there was something of the “thwarted fan” about Mr Kerar and Keane’s lawyer described the whole incident as a “storm in a teacup”.
Keane was cleared of causing harassment, alarm or distress to Mr Kerar — a public order offence.
Dismissing the case against Keane, the judge told him: “I have listened with great care to the evidence in your case. The burden of proof is on the prosecution.
“It’s my view, taking, as I have said, a careful account of the evidence, that they have failed to discharge their burden; therefore I find you not guilty.”
He added that the evidence was “riddled with inconsistencies and improbabilities”.
He told Keane: “You probably will regret getting out of the car.”
The defendant made no reaction as the verdict was given.
Keane told the court he did not flick a ‘V’ sign at Mr Kerar, who had accused him of swearing and staring at him as both were parked up in Altrincham, Cheshire on the morning of January 30 this year.
Football fan Mr Kerar, told the court “I love Roy Keane”, but claimed Keane gave him “bad looks”.
Mr Kerar said Keane later followed him in his car before flicking the ‘V’ sign, then getting out of his black Land Rover and approaching the cab, swearing at him. But from the witness box the former Ipswich and Sunderland manager denied any wrongdoing.
Keane said he was “chilling out, relaxing” in his car, waiting for his wife, when he noticed Mr Kerar across the road in his taxi.
Keane said they nodded to acknowledge each other but as they both moved off in their cars the cab driver made a gesture.
Keane, pushing the corners of his mouth up with his fingers, told the court: “He gave me a smirking gesture.” As Keane and his wife passed in his car, the witness said Mr Kerar gave him a “fake smirk” but he did not react.
He added: “I noticed in our mirror that the driver gave me two fingers.” Keane said he then got out of his car at a junction .
“I opened the door and literally asked him what’s his problem. I said it two or three times,” he said.
“He said something like ‘you need to cheer up’ — along them lines.
“I just turned and got back in my car. As I got back in my car with my back to him I said, ‘Oh fuck off’.”
Keane denied “repeatedly” swearing and gesturing with his arms.
Stuart Denney QC, defending, asked: “Mr Keane, what’s been suggested is that you were pretty much from the off behaving in an aggressive, violent manner. Any truth in that?”
Keane replied: “None whatsoever.” Mr Denney continued: “Did you have any reason to be aggressive?” “No,” replied Keane.
Mr Denney asked: “Anything in particular to be aggressive with at the world that morning?” Keane, with a short laugh, replied: “No. Not that morning.”
Earlier, Mr Kerar, who was allowed to give evidence from behind a screen, told the court he had pulled over to allow his passenger to get cash from a bank in Hale village.
He recognised Keane sitting in his black Land Rover across the road from him, adding: “I love Roy Keane and I love football.” However, he claimed the former player was staring at him.
“He was looking at me very aggressively, saying something in his car,” Mr Kerar said. “I couldn’t hear him. He was looking at me very aggressively. I have never met him before. He was giving me bad looks.”
He claimed that after both pulled off and went in the same direction, the clash at the junction occurred.
“He jumped from his car and he was swearing, aggressive.
“I could hear from him his Irish accent. He was very mad. He was swearing, mad and he lost his temper. He was very aggressive. He put his finger to me like that [gestured V sign].
“He was of course ‘fucking’ and ‘fucking’. “I’m not going to say what he said. He was swearing, ‘you fucking’ this, ‘you fuck’ that.
“I’m not sure exactly what he was saying. I said to him to go back to his car.” He told the court that he then went to Altrincham Police Station to report the matter and under cross-examination he admitted that he then rang the Manchester Evening News newspaper around 30 minutes after the incident.
Mr Kerar denied he was seeking publicity, telling the court: “I want this court to punish Roy Keane, what he did to me. I don’t want publicity.”
Keane left court accompanied by his legal team, without commenting on the verdict. Keane was awarded costs from central funds.
A legal source said that, as he was cleared, he would be eligible for some legal aid, amounting to around £1,000 (€1,400) of the estimated £5,000 legal costs.