Publicist JoAnn Geffen released a statement Tuesday evening saying Cassidy had died "surrounded by those he loved." No further details were immediately available, but Geffen said on Saturday that Cassidy was in a Fort Lauderdale, Florida, hospital suffering from organ failure.
The teen and pre-teen idol starred in the 1970s sitcom and sold millions of records as the musical group's lead singer.
"The Partridge Family" aired from 1970-74 and was intended at first as a vehicle for Shirley Jones, the Oscar winning actress and Cassidy's stepmother. Jones played Shirley Partridge, a widow with five children with whom she forms a popular act that travels on a psychedelic bus.