Indy 500 winner Takuma Sato will leave Andretti Racing after one season and return to Rahal Letterman Lanigan Racing in 2018.
The 40-year-old Sato became the first Japanese winner of the Indianapolis 500 this year and managed four top-five finishes and eighth overall in the standings.
He has close ties to engine supplier Honda and opted to shift to a team that had committed to the manufacturer while Andretti pondered its future.
"I'm excited about having Taku back with us," team co-owner Bobby Rahal told Motorsport.com. "I have such admiration for his spirit and how he approaches everything and was so happy for him when he won the Indy 500 this year.
"The chance to bring him back to the team was too good to pass up. He and Graham get along very well and we will have two strong cars that can win any race in 2018.
"I think that will give our team a great chance at being contenders in every race but it's also going to give each of our drivers a chance to have their best years ever.
"I'm excited about it and even though the 2017 season just concluded, I can't wait for the 2018 season to start."
Sato joins Graham Rahal at the two-car team.