In the second part of the final instalment of the series, which will be released next Summer, Grint and his co-stars have been aged for and epilogue set 19 years in the future.
"I don't age gracefully in the last film when all of us get older," he told Parade magazine. "My hair is still red but I have a lot less of it.
"It was quite a shock when I saw myself in the mirror. I felt like I was looking at Donald Trump because they gave me that comb-over that he has.
"I did get a lot of ribbing from everyone, I must admit."
Harry Potter and the Deathly Hallows: Part One opens in cinemas on November 19.