The talent executive died in Los Angeles on Monday (11Jun12). No further details of his death have been released.
He was hired as a booking agent for the MCA Talent Agency in the 1950s, and looked after the careers of big singers including Horne, Tony Bennett and Rosemary Clooney.
He then began representing movie stars including Brando, Garland and Ronald Reagan.
Barnett is survived by his six children. His wife, actress Isabel Bigley, passed away in 2006.