He started his acting career in the 1970s, and joined the Steppenwolf Theatre.
He also had roles in films such as Primal Fear and The Broken Hearts Club.
Born in Blackpool, England, Mahoney made Chicago his adopted home town.
After university in Illinois he joined the U.S. army to speed up his citizenship process before teaching English at Western Illinois University in the early 1970s and serving as the editor of a medical journal.
Mahoney, who was on the NBC sitcom for its entire 11-year run from 1993 to 2004, nabbed two Emmy nominations, losing to Pierce in 1999 and Brad Garrett ("Everybody Loves Raymond") in 2003, and two Golden Globe nominations, losing to Beau Bridges ("The Positively True Adventures of the Alleged Texas Cheerleader-Murdering Mom") in 1994 and to Robert Downey Jr. From there he went on to the film industry.More news: Autopsy planned on girl, 2, found on porch in freezing temps
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"It is with our deepest sorrow that we share the news that ensemble member of 39 years John Mahoney passed away". Most widely recognized as the face of Kelsey Grammer and David Hyde Pierce's father on Frasier, Mahoney brought warmth to an otherwise grumpy, sarcastic character. As a voice actor, Mahoney had roles in Antz, Atlantis: The Lost Empire and The Iron Giant.
Before Frasier, Mahoney could often be found on Chicago's big stages, even winning a Tony Award in 1986 for Broadway's The House of Blue Leaves.
He most recently appeared on TV screens in 2015, when he portrayed businessman Andrew Del Mar in an episode of ITV drama Foyle's War. His passing was announced by his manager and said he had died after a short illness. The cause of death was not immediately provided.
John was intensely private about his personal life, but is thought to have never married, despite previously claiming to have been in several relationships. At the age of 11, he visited his sister - a war bride living in IL - and returned to Chicago eight years later under his sister's sponsorship, becoming a United States citizen in 1959.
Frasier casting director Jeff Greenberg also saluted the late actor on Twitter, calling Mahoney an exceptionally kind man and a brilliant actor.