Frid died April 13 of natural causes at a hospital in his hometown of Hamilton, Canada, said Jim Pierson, a spokesman for Dan Curtis Productions, which produced"Dark Shadows."
Curtis intended Barnabas to be a short-term villain but soon realized that the Shakespearean actor "brought a very gothic, romantic quality" to the role, Curtis later said. Frid remained on the ABC show until it left the air in 1971.
When Frid was asked for his advice on developing the character, he later recalled saying, "Make him human. Remember he's real, and every monster is a human of sorts."
The series is credited with bringing the idea of a sympathetic vampire to the fore of popular entertainment. "Dark Shadows" is regarded as a precursor to the "Twilight" films and such contemporary television series as"The Vampire Diaries"and "True Blood."
"Without question, without the character of Barnabas Collins, you wouldn't have the vampires of today," Kathryn Leigh Scott, a regular on "Dark Shadows," told the Newark, N.J., Star-Ledger last year.
The show retains a devoted fan base, fueled by cable reruns and video collections.
The young viewers who made up the core audience are now aging baby boomers who wax nostalgic over the show, "inevitably noting that they used to rush home from school" to watch it, according to the 2009 book "The Essential Cult TV Reader."
One of them was Johnny Depp, who plays Barnabas in the Tim Burton-directed big-screen remake of "Dark Shadows" scheduled to open next month.
"Jonathan Frid was the reason I used to run home to watch 'Dark Shadows.' His elegance and grace was an inspiration then and will continue to remain one," Depp said in a statement to The Times. "When I had the honor to finally meet him … he was elegant and magical as I had always imagined."
Last year, Frid traveled to London to film his final screen role, a cameo in the "Dark Shadows" film.
Born Dec. 2, 1924, in Hamilton, Frid was the youngest of three brothers. He is survived by a nephew.
World War II interrupted his studies at Hamilton's McMaster University, and after serving in the Royal Canadian Navy he graduated in 1948. Frid attended the Royal Academy of Dramatic Art in London the next year and returned to Canada in the early 1950s.
After earning a master of fine arts in directing from Yale University's drama school in 1957, he appeared in many classical regional and touring productions. Twice in the late 1950s he shared the stage with Katharine Hepburn.
He played Barnabas Collins in the film "House of Dark Shadows" (1970), starred in the early Oliver Stone feature film "Seizure" (1974), and appeared in a late 1980s Broadway revival of"Arsenic and Old Lace."
Although Frid lamented that people always "expect to see the vampire," he began attending "Dark Shadows" conventions but developed a "reader's theater" short-story presentation that he performed instead of answering fans' "boring" questions. He toured the U.S. with the show until 1994, when he essentially retired and returned to Canada.
The popularity of the vampire that made him famous baffled Frid, who told The Times in 1991: "I guess there was something vulnerable about the character, if you accept the idiotic premise of coming out of a coffin after 175 years.... I was so humiliated all the time, maybe there was a bit of humility in my work."