The team announced he had cancer in March of 2014, and head coach Dave Cameron repeatedly asked for people to keep Reeds and his family in their thoughts.
"It is with very heavy hearts that all of us within the Senators family remember Mark who was truly a wonderful father, husband, player, coach and friend," owner Eugene Melnyk said in a statement. "Mark's charismatic fighting spirit was present right until the end. We are all better for having had the opportunity to work so closely with Mark whose passion for life, hockey and his family will leave an indelible mark on our organization.