A Toronto Blue Jays spokesman confirmed Saturday that Fanning died, but had no other details. Fanning recently worked as an ambassador for the team.
"It is with my deepest condolences to the Fanning family upon hearing of the passing of Jim today," Blue Jays president and CEO Paul Beeston said in a statement. "He was a longtime friend and not enough can be said of his contributions to the game of baseball, particularly in Canada.
"Jim impacted many lives and he will be remembered fondly by many inside and outside the game of baseball."
Fanning was named the Expos' first GM in August 1968 and spent 25 years with the franchise that moved to Washington in 2005 and became the Nationals. He served as vice-president, scout and had two stints as field manager (1981-'82, '84), compiling a 116-103 career record as skipper.
In the strike-shortened 1981 season, Fanning guided Montreal to the playoffs. After beating Philadelphia, the Expos lost to Los Angeles in the National League Championship Series.
The Chicago native was a backup catcher with the Chicago Cubs from 1954-57, hitting .170 with five RBIs in 64 games. He later moved into management roles at the minor-league level before becoming a special assignment scout for the Milwaukee Braves in 1963.
Fanning was promoted to assistant GM the next year and held that position until 1967.
Fanning was hired to be the first scouting director of Major League Baseball’s Scouting Bureau in 1968 but left that position for the GM job in Montreal. In his long run with the Expos, Fanning established himself as a top talent evaluator and signed players such as Larry Walker, Andres Galarraga and Randy Johnson.
He left Montreal in 1993 and was later hired as a special assignment scout with the Colorado Rockies.
Fanning became an ambassador for the Blue Jays in early 2000.
"He was dedicated to developing baseball in Canada," said former Blue Jays GM Gord Ash, now vice president and assistant GM of the Milwaukee Brewers. "He was a great ambassador. He made Canada his home, he was available and wanted to participate.
"I think everyone's favourite memory of Jim is just his demeanour," Ash added. "He had a very welcoming type of personality. Everybody liked him, everybody got along with him easily."
Fanning, a resident of London, Ont., was inducted into the Canadian Baseball Hall of Fame in 2000. He became a Canadian citizen in 2012.
"We have lost a baseball legend and one of the nicest people you will ever meet," Hall director Scott Crawford said in an email.
With files from The Associated Press.