The District 9 star praised his director, describing him as an "artist", and insisted that the remake was not developed for commercial reasons.
"It's such a good story. Something like this only comes along very rarely, and it seems perfectly reasonable to have a reimagining of it," he told Empire.
"Very often Hollywood will remake something just because there's a built-in audience, just for the commercial aspect of doing it. That's fair enough, I guess. But with this, if you look at the people who have got involved, it's more for the creative drive."
He added: "It's not a massive franchise that you're trying to reboot or something that's going to make a gazillion dollars. It's just a film that's artistically inspiring to people.
"Spike is an artist who's been inspired to do it. The drive behind it isn't a studio or an executive thinking it's a great marketing opportunity. The drive behind it for the producers and the actors and the director, is simply the inspiration of the story.
"You'll notice it's not a project populated with people who are known for only taking jobs because they're commercial."
Elizabeth Olsen, Josh Brolin and Samuel L Jackson will also star in the movie, which is based on Chan-wook Park's South Korean original.
Oldboy arrives in US cinemas on October 11 next year. Watch Olsen discuss the film with Digital Spy below: