John Hanna spent six years in the NHL with New York, Montreal, and Philadelphia. He later played for the Cleveland Crusaders of the WHA where he was a first team all-star. His playing career came to an abrupt end in 1973 when he broke his leg and was forced into retirement.

He was named coach of the Crusaders top farm club in Jacksonville and coached the parent club Crusaders in 1974-75. He later went on to coach the Springfield Indians of the AHL but had to vacate the position as a result of being hit by a car on the way to training camp in 1976.

Hanna is proud of his hockey career as a rugged defenceman for the six teams in the NHL and the AHL, where the calibre was higher than some of the teams in the now expanded NHL. John Hanna was inducted into the Nova Scotia Sport Hall of Fame in 1980.