Trump addressed the notion as he left the White House Friday for the G7 summit in Canada.
"He was not very popular then, his memory is very popular now," Trump said. "I'm thinking about [a pardon] very seriously."
Ali's attorney Ron Tweel, however, said a pardon would serve no purpose.
"We appreciate President Trump's sentiment, but a pardon is unnecessary," he said. "The U.S. Supreme Court overturned the conviction of Muhammad Ali in a unanimous decision in 1971. There is no conviction from which a pardon is needed."
Ali refused induction into the U.S. Army in 1965 and was later convicted of draft evasion and sentenced to five years in prison. He was stripped of his heavyweight title and banned from boxing for declaring himself a conscientious objector and citing his Muslim faith.
"I'm not going ten thousand miles from home to help murder and burn another poor nation simply to continue the domination of white slave masters of the darker people the world over," Ali said at the time. "This is the day when such evils must come to an end."
Ali remained out of prison during his appeal until the conviction was overturned by the high court. He died in 2016 at the age of 74.
The president has also pardoned conservative filmmaker Dinesh D'Souza, who pleaded guilty in 2014 to violating campaign finance laws, former Arizona sheriff Joe Arpaio and former White House aide I. Lewis "Scooter" Libby.