The footballer, who now plays for Nottingham Forest, said he was acting in self defence when he threw two punches at John Bell, who suffered a fractured his cheek bone and cut to his eye socket.
Henderson's evening out with his then girlfriend Lucy Caplan was ruined when they were confronted by a woman, who repeatedly claimed she had sex with him.
Before the start of his trial at St Albans crown court, potential jurors were asked by the judge if they were active supporters of, or had allegiance against Watford, Millwall or Nottingham Forest - Henderson's previous teams and his current side.
It was the third time a jury had been called to hear the case. On the first occasion a witness was unavailable and on the second the jury could not reach a verdict.
Today the third jury unanimously cleared Henderson, 32, of inflicting grievous bodily harm on John Bell on 1 January 2012.
Prosecutor Alan Richards said Henderson and Lucy Caplan had enjoyed a meal at Darcy's restaurant in St Albans before going into the bar where they encountered 48-year-old Hazel Kent.
She was not known to either the footballer, his girlfriend or Mr Bell, his partner John Lavelle and two women friends, who were also in the bar.
Mr Richards said Ms Kent was "responsible for sowing seeds of tension." He went on: "For reasons best known to herself, Ms Kent behaved somewhat unpleasantly towards Mr Henderson and Miss Caplan, asserting on more than one occasion, in Miss Caplan's presence, that she had recently had sex with Mr Henderson.
"Ms Kent claimed that she could describe Mr Henderson's home in Markyate, Herts and correctly identified the brand of his boxer shorts.
"Understandably this upset Miss Caplan and perhaps caused some tension between her and Mr Henderson. Equally understandably, Mr Henderson was keen that Ms Kent should leave him and Miss Caplan alone."
She told Ms Caplan: "I am an escort. I knew what your house looks like inside I have f..... your boyfriend."
"There is no reason to believe that this was anything other than pure fiction," Mr Richards told the jury of 5 men and 7 women.
Henderson told the jury at first he had laughed at what Ms Kent was alleging, telling the jury there was absolutely not truth in it and that he had never met met her before.
The footballer and Mr Bell, 42, did not know each other, but earlier in the evening Mr Bell has been given a cigarette by the footballer's girlfriend as they stood outside the restaurant.
They had spoken on two earlier occasions that night. When Mr Bell discovered Henderson was playing for Millwall Mr Bell asked him: "Aren't they a bit s...?"
After the confrontation with Ms Kent, Lucy Caplan, who had been bought a Hermes handbag and a bracelet by the footballer for Christmas, was upset and left the bar.
Mr Bell, now 42, then walked over to talk to Darius Henderson again.
CCTV played to the court showed Mr Bell, who admitted he was drunk, appeared to be unsteady on his feet. Henderson was seen to throw two punches.
The footballer told the jury he thought he was going to be hit and that he acted in self-defence. Asked how he felt when his girlfriend walked out in a distressed state he said: "I was frustrated, very tired, stunned and shocked that the evening had ended so badly."
He said it seemed that Ms Kent had brought John Bell over to him just before he hit him. "They walked from the same area and exchanged a bottle of champagne."
He went on: "He said: 'I am going to make you apologise.' Even though he was smaller than me I was worried about what he was going to do. He put his head next to mine. I stood up to push him away.
Asked by his barrister Sean Minihan why he threw a second punch, he said: "In my opinion he was still a threat."
Recorder Simon Sterling told Henderson, who had his head in his hands, that he was free to go. He granted him a costs order, meaning that his legal fees will be paid.
Henderson was too upset to talk after the jury returned its verdict.