John Hillerman, the Texas-born actor who played a likably snobbish British caretaker on the hit television show “Magnum, P.I.” and had supporting roles in celebrated 1970s movies like “Chinatown” and “Blazing Saddles,” died on Thursday at his home in Houston. He was 84.

His publicist, Lori De Waal, confirmed his death. She did not specify the cause.

After 30 years of acting on Broadway and in Hollywood, Mr. Hillerman landed a career-defining role in 1980 as Jonathan Quayle Higgins III, the stuffy perfectionist and foil to the free-spirited detective Thomas Magnum, played by Tom Selleck, on the CBS series “Magnum, P.I.” Higgins, the haughty major-domo of the beachfront property where Magnum lived, was grouchy with a sarcastic wit, not unlike the detective Mr. Hillerman had played on the mid-1970s show “Ellery Queen.”

“Magnum, P.I.” became a runaway success and ran for eight years. It made Mr. Selleck a star and a tabloid mainstay, solidifying his Hollywood career. But Mr. Hillerman found his supporting role equally rewarding.

“It isn’t so long ago that I was a struggling actor living in New York,” Mr. Hillerman said in a 1985 interview as he sipped a glass of wine on his penthouse balcony in Honolulu, “and the only thing I could overlook was my rent.”