Terry, 21, wept as he told the jury he did not attack doorman Trevor Thirlwell, 28, at the exclusive Wellington nightclub in Knightsbridge, central London, on January 4, 2002.
After two-and-a-half hours in the witness box Terry buried his head in his right hand and began wiping away tears.
Judge Fabyan Evans asked the former England Under-21 captain if he would like a break until after lunch and Terry said he would.
Spiky-haired Terry, wearing a dark suit and tie, was barely audible at times and was repeatedly told to speak up by his counsel, Desmond De Silva, QC.
The footballer told the court he had only met Dublin-born Wimbledon player Des Byrne once before they went to the club on January 4.
Byrne was a friend of his Chelsea team-mate Jody Morris and the three players had been to eat at Yates Restaurant in Epsom, Surrey, before making a spur-of-the-moment decision to go into central London.
Terry had just bought a new car and allowed Byrne to drive it.
They went first to a club in Tottenham Court Road but it was closed so they drove to The Wellington because Morris knew the owner.
Terry denied behaving loutishly in the club.
The three players were asked to go upstairs from the basement bar to reception after Morris allegedly told the manageress to "f*** off."
Terry said he never heard the remark but apologised to the manageress on behalf of Morris anyway.
When he got to reception he admitted asking for the autograph of actor Danny Dyer, who was passing through and then scrunching it up and throwing it on the floor.
But he said: "It was just a joke between myself and Des, the guy had already left."
Terry continued: "After the autograph Des gave the pen back to the reception guy and something was said...I don't know what, but Des was asked to leave and we were ushered out."
He said the three players were outside trying to call a taxi.
Morris wanted to make sure there was no problem coming back to the club in the future and he and Byrne were asking for the owner and the fight started shortly after that, Terry said.
Terry said: "Des went up to the doorman asking if he could go and see Jake and Trevor Thirlwall said 'just f*** off you Irish pr***k' and that's when the mood changed for me."
There was then a "scuffle" during which the bouncer threw a punch at Byrne.
He said: "Looking in I could see Des was getting ganged up on by two or three people in the reception area, I saw him punched to the floor and he was getting kicked by the young reception guy."
The man in reception he later identified as Matthew Thirlwall.
Terry said he went in again to try to "save" Byrne, demonstrating to the court how he used his arms to push people apart and then the fracas spilled outside.
He said Byrne was punched and knocked to the ground by Matthew Thirlwall and Trevor Thirlwall was kneeling over him ready to punch him.
"I thought it was two on one and that's unfair. I had seen the young reception guy kick Des and I thought he was going to kick him again so I ran over and got Matthew Thirlwall off him," he said.
"That's when the three of them ganged up on me and started to attack me, it was mainly Matthew Thirlwall and Trevor Thirlwall."
Terry then demonstrated the punch he threw at Trevor Thirlwall, a straight jab with his right hand.
"It was fairly hard. As far as I remember it hit him in his head, his face.
"The sole purpose was to get people off. I was being attacked by two if not three of them."
Former Olympic decathlon champion Daley Thompson appeared as a character witness for Des Byrne.
Mr Thompson told the court he worked as a fitness coach at Wimbledon FC where Byrne has been a player for more than two years.
"He's like a young puppy, he just wants to get on and be really good. His application has always been exemplary, he always gives a hundred percent."