The jury in Nevada says Gavin Cox caused his own injuries during the famous vanishing act at a show in Las Vegas in 2013.
Mr Cox filed a negligence lawsuit after falling during the show. He said he suffered brain and other injuries.
The ruling means that he cannot seek financial damages from the illusionist.
Mr Copperfield, the world's highest paid magician, has performed the "Lucky#13" trick thousands of times without any problems.
The illusion involves making 13 audience members - chosen at random - disappear on stage.
The grand surprise comes when the illusionist reveals the 13 at the back of the auditorium.
Last month, Mr Copperfield was forced to reveal in court that after curtains come down on the participants on stage, they are hurried through passageways that lead them around the Las Vegas MGM resort.
They leave the building and enter again at the back of the theatre.
Mr Cox, a 58-year-old from Kent, fell while being led through these passages by stagehands. He was taken to hospital with a dislocated shoulder.
He said doctors later diagnosed a brain lesion.
Mr Cox's lawsuit claimed he had spent more than $400,000 (£302,000) on medical bills.
It alleged there was construction debris in the passageways he used, but Mr Copperfield said he walked the same path earlier and it was clear.
The Las Vegas resort MGM and Mr Copperfield's company were also defendants in the lawsuit.
They were also found negligent - but not financially liable for Mr Cox's injuries.
More about: DavidCopperfield
