Reardon was known as a tough defenceman, a physical player who exhibited great endurance by continuing to play while injured. He played two seasons with Montreal before enlisting in the Canadian Army in 1942. He spent several years playing for army teams in the Ottawa area, winning the Allan Cup with the Commandos in 1943 before he was shipped overseas. Following World War II, Reardon returned to the Canadiens and won the Stanley Cup in 1946. He retired prior to turning 30, a probable result of the numerous injuries he sustained.
Reardon continued his hockey career off-ice, becoming a successful executive in hockey, primarily with the Canadiens. After scouting and managing farm teams to many minor league championships, he earned the position as the Canadiens vice-president. During his tenure with Montreal the team won five Stanley Cup titles. He was inducted into the Hall of Fame in 1966.