The actor, 31, portrayed the late King of rock 'n' roll in biopic Elvis, and has been nominated for an Academy Award for his performance.
Fans have raved about how Butler slipped into character – but some were confused by the fact his accent seemed to linger after the cameras stopped rolling.
Speaking on The Graham Norton Show, he explained why he still sounds a little like Elvis, saying: “I am getting rid of the accent, but I have probably damaged my vocal cords with all that singing.
“One song took 40 takes!”
The actor also said starring in the film and getting the Oscar nod had been “a whirlwind”.
“It’s amazing because when you are making a film you never really know how it will be received,” he said.
“With this one there were so many ways it could go wrong so to be received in the way it has means the world to me.”
The movie also stars Tom Hanks as Elvis’s manager Colonel Parker.
Butler said of working with the A-lister: “I had no idea what it was going to be like meeting someone you have admired for so long.
"You hope they would be warm to you, but you never really know."
He went on: "He is such a master of his craft, and I was intimidated, but the first time I met him he gave me the biggest bear hug and joked about how nervous he was.
"When I said I was terrified, he said ‘And, nobody knows what Colonel Parker sounds like, but everyone knows what Elvis sounds like!’”
The Graham Norton Show is on BBC One on Friday 3 February at 10.40pm. It is also available on BBC iPlayer.
Watch: Austin Butler reflects on Lisa Marie Presley bond