The Phillies announced Montgomery's death, citing his five-year battle against cancer. Montgomery joined the Phillies franchise in 1971, working in the ticket office and helping operate the scoreboard.
"David was one of Philadelphia's most influential business and civic leaders in his generation," Phillies managing partner John Middleton said in a news release. "For 25 years, he has been an invaluable business partner and, more importantly, an invaluable friend. He was beloved by everyone at the Phillies. Leigh and I are saddened beyond words at David's passing and extend our love and sympathy to [his wife] Lyn, his children and grandchildren."
Montgomery was named marketing director and director of sales before being promoted to executive vice president in 1981. He became the Phillies' chief operating officer in 1992 until he was promoted to general partner, president and chief executive officer in 1997.
He was diagnosed with cancer in May 2014 and took a leave of absence in August that year. He returned to his job in January 2015 and remained active in the role until his death.
Montgomery is survived by wife, three children and three grandchildren. Funeral arrangements were incomplete.