The 73-year-old, already serving a jail sentence for historic sex offences against young women, showed little emotion as the jury foreman returned the verdict.
Clifford had always denied the offence, having been accused by prosecutors of using “his position of power” to “humiliate” a 17-year-old girl into performing a sex act on him in the 1980s.
Clifford, formerly of Hersham, Surrey, was jailed for eight years in May 2014 after being convicted of eight charges under Operation Yewtree, the Metropolitan Police inquiry set up after the Jimmy Savile scandal.
The jury took five hours and 50 minutes to find him not guilty.
Clifford, wearing a blue suit and open-neck white shirt, and shorn of the white beard he sported earlier in the trial, smiled briefly and winked in the direction of his daughter, who was in the public gallery.
He also gestured a ‘thank you’ with his hand to his counsel and a supporter, before being taken back into custody to continue his existing prison sentence.
The trial was told that Clifford — who previously worked with the likes of boxer Muhammad Ali, The Beatles, and golfer Seve Ballesteros, as well as fame-hungry wannabes — was alleged to have locked the 17-year-old in his London office and forced her to engage in a sexual act with him.
However, Clifford said the incident did not happen and that he was having regular sex with a French model at the time — one of three long-term extramarital affairs he had during a two-decade period.
Giving evidence in his defence, Clifford said his previous convictions — which he continued to deny — made him “an easy target”.
He said: “I was found guilty [in 2014] ... I know I’m innocent. Hopefully one day I will be able to prove that.
“One of the things I’ve learned [from the last trial] is you’re guilty until proven innocent when sexual offences are involved.”
During the trial, Clifford was held in Wandsworth Prison in south London, but is now expected to return to category C Littlehey Prison in East Anglia, where he told the court he has been playing tennis, softball, and writing a new book.