Allen served as Philadelphia's GM from 1969-83 and was the architect of its only two Stanley Cup-winning squads in 1973-74 and 1974-75.
The Flyers, who became known as the Broadstreet Bullies for their rough style of play during his tenure, also reached the Stanley Cup finals in 1976 1980.
The Saskatoon, Saskatoon, native was the expansion Flyers' head coach during their first two years in the NHL, 1967-69, before moving to the front office.
He was credited with using a series of shrewd trades at the expense of competitors to quickly transform the new franchise into a perennial contender, earning the nickname "Thief."
"Keith was the first coach in the history of the Philadelphia Flyers and a man for whom I have tremendous respect," Flyers Chairman Ed Snider said in statement.
Allen was a professional player for 18 years. His only NHL exposure came with the Detroit Red Wings for two years in the 1950s.
Allen, who was elected to the Hockey Hall of Fame in the builder's category in 1992, is survived by his wife Joyce, sons Brad and Blake and daughter Traci.