The British-born Mahoney was best known for his role as Martin Crane on Frasier, the cranky father to Niles and the title character. The long-running Cheers spinoff was on the air from 1993 until 2004.
In addition to two Emmy nominations for his role on Frasier, Mahoney also received a Tony Award in 1986 for his performance in The House of Blue Leaves.
More recently, the actor made appearances on In Treatment, Burn Notice, Hot in Cleveland and Foyle's War.
He was also a member of Chicago's Steppenwolf Theatre Company since 1979. Yesterday's (February 5) performance of the The Herd was cancelled in his honour.
See a selection of social media tributes to the late Mahoney below.
He always said - it took him a long time to find out what he loved - and he loved performing - he was so happy to be there - he made everyone around him better and happier each day - blessed to know him https://t.co/d7UKnCzB6c— John Cusack (@johncusack) February 6, 2018
I have looked up to #JohnMahoney for so many years for so many reasons. He has always been an inspiration to me. He will continue to be.❤️— Jesse Tyler Ferguson (@jessetyler) February 6, 2018