An official from the medical examiner's office in Martin County, Fla., confirmed to the celebrity-news website that it had received a call from Martin Memorial Hospital that Jones had died.
Jones suffered a heart attack at his home and was taken to a hospital, where he was pronounced dead, a representative for the singer told TMZ.
The singer is survived by his wife, Jessica, and four daughters from two previous marriages..
Jones, who was born in England, joined the three other Monkees -- Americans Mickey Dolenz, Michael Nesmith and Peter Tork -- in 1965. Together they churned out a bunch of hugely popular songs including three No. 1 hits -- Daydream Believer, Last Train to Clarksville and I'm a Believer.
The group was initially cast by TV producers who wanted to create a scripted series about an actual rock 'n' roll band in the mold of the Beatles. But the group exploded, and Jones in particular became a Beatles-caliber heartthrob.
Jones's last performance was Feb. 19 in Oklahoma; the previous night, he performed Daydream Believer and It's Nice to Be With You at B.B. King Blues Club in New York City.