Michael Baigent and Richard Leigh, who wrote "The Holy Blood and the Holy Grail" had sued Random House, publisher of both books, claiming Brown copied the "central theme" of their book.
In his ruling, Justice Peter Smith said Baigent and Leigh's book did not have a central theme, the BBC reported.
"It was an artificial creation for the purposes of the litigation working back from 'The Da Vinci Code,'" he ruled.
Brown, who denied copying the work during the trial, said the verdict "shows that this claim was utterly without merit" and he can now concentrate on writing his novel.
"We are pleased that justice -- and common sense -- have prevailed," said Random House Chief Executive Gail Rebuck.
Friday's ruling clears the way for the May release of Ron Howard's film adaptation of "The Da Vinci Code."