The actor, who plays Draco Malfoy in the saga, told Lopez Tonight that he and co-star Daniel Radcliffe got "heated" over the board game after the wrap party.
Felton said: "They threw a massive party at the studios where we shoot. They built a carnival with theme park rides and things like that, so it was a good way to see it through.
"There was an after, after party, if you will, and we had a few of the cast members there. Everyone was expecting us to be popping Cristal and all the rest of it but we actually played Scrabble until about two in the morning; Daniel [Radcliffe] and I got very heated at a game of Scrabble!"
George Lopez then joked: "So you and Daniel played Scrabble into the wee hours of the night?... You see, nerds?! Celebrate!"
Felton agreed: "Absolutely, it's one of the best games invented. I loved it."
During the interview, Felton also admitted that he hasn't seen his new movie Rise of the Planet of the Apes yet, joking that he was "very jealous" when Lopez revealed that he had.
"It's scary and your character is the best character in the movie... and there is no accent!" said Lopez, in reference to Felton adopting an American accent for the film.
"I went Californian for a few weeks which was fun," said Felton. "It was great."
Harry Potter is in cinemas now. Rise of the Planet of the Apes opens August 5 in the US and August 12 in the UK.
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Watch a teaser trailer for Rise of the Planet of the Apes below: