The Scot, who also played for Rotherham and Burnley, made 445 appearances for Bristol City, becoming a club legend, before joining Manchester City in 1981.
After making his debut in 1970, Gow helped Bristol City win promotion to the old First Division in 1976.
He scored twice in Manchester City's run to the famous FA Cup final of 1981.
"Everyone at the club sends its condolences to Gerry's family and friends at this sad time," a Bristol City statement said.
Gow ended his playing career as player-manager at then non-league Yeovil Town, where he was in charge from 1984 to 1987.
A statement from Manchester City said: "Everyone at Manchester City FC is saddened to learn of the passing of Gerry Gow at the age of 64 following his brave battle with illness.
"A cult hero in his short spell at Maine Road in the eighties, Gow made 36 appearances for the Blues between 1981 and 1982."
Gow joined Rotherham after leaving Maine Road in 1982 before a short spell at Burnley.
A statement on the Millers' website added: "Rotherham United are deeply saddened to learn of the passing of former midfielder Gerry Gow. Once a Miller, always a Miller."
Former Bristol City and Manchester City midfielder and Yeovil Town player-boss Gerry Gow has died aged 64 after being diagnosed with cancer this year.