This is the first major overhaul of the 41-year-old company's fries, although it has adjusted the recipe in the past.
The new fries start appearing on Thursday and roll out over the next two weeks.
They're slightly slimmer than the old recipe, and crispier because they're smaller.
Chief Marketing Officer Ken Calwell says people want more natural foods and they want to know where they come from.
He says having the skin on is a way to remind people that fries do come from potatoes.