Newfoundland MP Scott Simms, who knew Mifflin, said he died in Ottawa with his wife at his side.
Mifflin was first elected in 1988 representing the Newfoundland riding of Bonavista-Trinity-Conception after a distinguished 32-year career in the military, rising to the rank of rear admiral.
He was appointed minister of fisheries by then prime minister Jean Chretien in 1996. A year later, he was made minister of veterans affairs.
He was dropped from cabinet in 1999 after announcing he would not seek re-election.
Simms described him as a man of sound judgment who was not overly partisan.
Current Liberal Leader Justin Trudeau remarked on his passing on Twitter.
"Sad to hear about the passing of former MP and Minister Fred Mifflin," he wrote. "My thoughts are with his loved ones."
A funeral has been planned for Friday in Ottawa.