Andretti will reduce their presence on next season’s grid from four to three cars – and have confirmed that ex-F1 driver Grosjean will no longer figure for them.
The driver published an open letter on social media: “I enjoyed working with the IndyCar team at Andretti Autosport.
“I am proud of the successes we shared through two seasons. I am thankful for the many friendships developed at the highest level of American open-wheel racing.
“I had expected to continue racing with the fine people of Andretti Autosport in the coming years.
“I am disappointed that is not being fulfilled, and wish Andretti team members well. I am pursuing other options to continue my IndyCar career in pursuit of excellence.
“I have commenced an arbitration proceeding in Indiana against Andretti Autosport, seeking to protect my rights. I am represented by John Maley and Mark Owens of Barnes & Thornburg, LLP.
“Respectfully, Romain Grosjean.”
Grosjean has raced in IndyCar for three seasons since his F1 career ended in a dramatic fireball incident in Bahrain.
He first represented Dale Coyne Racing before switching to Andretti, where he delivered a pair of second-placed finishes earlier this year.
But those highs were few and far between, and Andretti have since signed Marcus Ericsson.
“I do have other IndyCar teams that are talking to me. I will land on my feet,” he has said.