Andrew Symeou, 22, from Enfield, north London, was extradited to Greece in 2009 to face charges over the death in Zante of Jonathan Hiles, 18, from Cardiff.
The Londoner was held in “one of Europe’s worst prisons” for 10 months before being bailed. A prosecutor recommended that he should be acquitted and a jury returned a not guilty verdict, campaign group Fair Trials International said.
Mr Symeou said: “There are no winners or losers, only pursuit of the truth. Today’s verdict has only stopped further injustice and a gross miscarriage of justice.
“I was not involved in any way in the death of Jonathan Hiles and the court agrees. I can finally return home and begin building my life again.”
Mr Symeou was accused of punching the teenager in the face, knocking him out in the process and causing him to fall from a dance podium in July 2007.
Mr Hiles suffered a severe brain injury and died two days later.
Fair Trials International claimed much of the apparent evidence against Mr Symeou, who denies being in the nightclub at the time, was based on information extracted by Greek police officers who intimidated witnesses.
The chief executive of Fair Trials International, Jago Russell, said: “Andrew Symeou is an innocent man who was condemned by failures in Europe’s justice systems to a four-year nightmare.
“While his friends were free to start their adult lives, Andrew was being dragged before the British courts, shipped off to a foreign land and held behind bars in one of Europe’s worst prisons.
“As the Symeous finally return home to start picking up the pieces, politicians in London and Brussels, with the power to build a better justice system in Europe, must not forget the ordeal this family has suffered.”