The jury of nine men and three women took four-and-a-half hours to reach their unanimous verdict at London's High Court.
Polanski was absent because of his fear of extradition to the US following his flight from the country in 1978 while awaiting sentence for having sex with a 13-year-old girl.
Although unseen, he was following proceedings via videolink from Paris.
He sued Conde Nast over a July 2002 Vanity Fair story which said that in the aftermath of the August 1969 murder of 26-year-old Tate and four others by Charles Manson's "Family", he made a pass at a woman in Elaine's restaurant in New York.
It recounted an onlooker, Lewis Lapham, as saying: "Fascinated by his performance, I watched as he slid his hand inside her thigh and began a long honeyed spiel which ended with the promise 'And I will make another Sharon Tate out of you'."
Polanski's lawyers said the article meant that he had gone "on the pull" and exploited the name of his late wife, who was eight months pregnant, as a "tool of seduction".
Polanski, backed up by actress Mia Farrow, said the incident never happened.
The magazine said its article was substantially true but accepted that the incident did not occur when Polanski was on his way back to Hollywood for Miss Tate's funeral - it maintained it took place about two weeks later.
It argued that, in any case, Polanski should not receive any damages as his reputation had already been ruined by his 1977 conviction and promiscuous past.
Its editor, Graydon Carter, shook his head at the verdict while Miss Tate's sister, Debra, smiled.