The Montreal Canadiens said Tuesday that Jean Beliveau suffered a stroke on Monday evening and was admitted to hospital.
The team added that Beliveau, 80, is undergoing active investigation and treatments and the Hall of Famer has asked everyone to respect his privacy and that of his family.
Beliveau, a 17-time Stanley Cup champion as a player and front office executive with the Canadiens, also has a surgical procedure last June to repair abdominal aneurysms.
Beliveau, who played all 20 of his NHL seasons with the Canadiens, captained the team for 10 seasons - longer than any other player in team history. He captained them to five Stanley Cup titles and in 1965 was named the first-ever recipient of the Conn Smythe trophy.
The Hockey Hall of Fame waived the three-year waiting period after his retirement in 1971 and immediately inducted him.