"The circumstances would have to be pretty extraordinary," the 26-year-old told the Radio Times.
"But then I am sure Harrison Ford said that with Han Solo [in Star Wars], and look what happened there."
Radcliffe, who appeared in eight Harry Potter films, said he was "saying 'No' for now" but added he was "leaving room to backtrack in the future".
The British actor will shortly be seen as a magician in Now You See Me 2, the sequel to the 2013 film about a team of bank-robbing illusionists.
In the film, out in the UK on 4 July, Radcliffe plays the card-sharp son of the character whom Sir Michael Caine played in the original.
The actor said it had not initially occurred to him that the film, which also stars Jesse Eisenberg and Woody Harrelson, would invite comparisons with the boy wizard role for which he remains best known.
"I actually didn't consider the connection to magic until somebody pointed it out to me," Radcliffe is quoted as saying.
"They were like, 'You are going to get loads of questions about magic again,' and I went, 'Oh, damn, I guess I am!'"
Ford, 73, was seen last year reprising his Han Solo role from the original Star Wars trilogy in Star Wars: The Force Awakens.
A two-part continuation to JK Rowling's Potter saga, Harry Potter and the Cursed Child, recently opened in London's West End.
Harry Potter star Daniel Radcliffe has said he would not rule out a return to the character, if the script was right.