A written statement from his office says the Hamilton businessman and philanthropist resigned effective Nov. 30.
No reason was given for his departure and his office did not immediately respond to a request for comment.
But in an interview with the Hamilton Spectator, the 72-year-old said he wants to spend more time with his family while he's still healthy.
"I guess my wife wants to spend a little more time in Florida and I had cataract surgery last week," Braley said. "I'm 72 and a half and healthy. I want to stay that way."
The Senate expenses scandal that has engulfed the chamber for a year may also have played a role in his decision.
Earlier this fall, Braley mentioned the scandal while acknowledging that he was thinking of leaving early.
"There are four people who are causing the problems for the other 100 senators," he told hamiltonnews.com, referring to senators Mike Duffy, Pamela Wallin, Patrick Brazeau and Mac Harb, whose questioned expense claims are under RCMP investigation.
"We are being tarred and feathered."
Braley, who owns the British Columbia Lions and Toronto Argonauts of the Canadian Football League, was named to the Senate by Prime Minister Stephen Harper in May 2010. He could have stayed until his 75th birthday in 2016.
In addition to being a successful businessman, Braley has been deeply involved in sports in Hamilton.
Braley was chairman of the 2003 World Cycling Championships there and was a director of Ontario’s successful bid to host the 2015 Pan Am Games. He quit the latter post when he was named to the Senate.
He has also served on the CFL's board of governors and was league's interim commissioner from March to November 2002.
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