The actor, who played the dad in the family favourite movie, was found dead in a hotel room by a maid.
TMZ reports: “Police were called to the hotel for a report of a medical emergency, but he was pronounced dead on the scene.
“The coroner is investigating, and cause of death is unclear at this time.”
The news outlet also reports that his rep revealed the star had “minor back surgery” on Wednesday at the Stanford Medical Center and was staying at the hotel in Palo Alto, California while he recovered.
John was known for playing Peter McAllister, Kevin’s dad in the iconic 90s trilogy.
He also starred in Beaches, Gladiator and The Sopranos, for which he was nominated for an Emmy.
John was still actively working and had six movies in development.
John was married three times; to Margot Kidder from 1979 until 1980, Sharon Heard from 1988 to 1996 and Lana Pritchard from May to December 2010.
He was also in a relationship with Melissa Leo and they have a son John together.
Heard and his second wife Sharon have two children together, son Max and a daughter named Annika.
When asked about his career, he admitted he lost out on roles because of his behaviour.
He said: “I guess I went from being a young leading man to being just kind of a hack actor. … When I came to Hollywood, I was pretty much a stage actor, and I expected everybody to be quiet. And they weren’t.
“They were doing their job, and you’re expected to do your job, and you’re sort of this ongoing co-existence. I was a little bit of an arrogant jerk.
“Now, it’s a little bit more like, ‘Okay, I realize you have to pat me down with powder every three seconds.’ And I stand there, and I’m a little more tolerant…. I think I had my time.
“I dropped the ball, as my father would say. I think I could have done more with my career than I did, and I sort of got sidetracked. But that’s OK, that’s all right, that’s the way it is. No sour grapes. I mean, I don’t have any regrets. Except that I could have played some bigger parts.”