It was confirmed on Wednesday that Rossi will leave Andretti Autosport after scoring seven wins, including the 2016 Indianapolis 500, in his seven seasons with the team.
The 30-year-old, who will be replaced at Andretti by Kyle Kirkwood, will join Pato O'Ward at Arrow McLaren SP after the Mexican's contract at the team was extended to 2025.
It has not yet confirmed publicly whether Rossi is the team’s third driver to supplement O’Ward and Felix Rosenqvist, or whether Rossi is replacing Rosenqvist in the #7 AMSP-Chevrolet with a third driver yet to be nominated.
Rossi has twice finished in the top three in points, but hasn't won a race since the 2019 season. He confirmed to Autosport last month that his key priority with his latest deal was to win the championship, stating his belief that only three teams in the series are capable of achieving that feat.
He said: “First, I want to thank everyone at Andretti Autosport for an incredible seven years. It has been a great ride with an awesome team, and it has been an honour to race for the Andretti name and for Michael for so long.
“The time has come for a new challenge, with a team that is growing in the sport. I look forward to contributing to the development of Arrow McLaren SP and helping them reach the top.
“I see the commitment this team has to each other and to me, and I’m looking forward to getting started. It’s time for me to race for another one of motorsport’s biggest names: McLaren.”
AMSP president Taylor Kiel stated: “As we look forward to 2023, we are looking for a driver that will be a great fit and bring experience to the team. Alex is a driver who knows what it takes to succeed in this sport and will strengthen our talented driver line-up.
“He shares the same winning mindset that I see every day across Arrow McLaren SP and I think we will find a lot of success together in the years to come.”
McLaren Racing CEO Zak Brown added that Rossi was “someone we have had our eye on for some time”.
“Alex is a proven race winner and an Indianapolis 500 champion, who shares our desire to win,” said Brown.
“It is essential that we put the right talent in place, both inside and outside the car, so we can consistently compete for championships and race wins as a team.
“We’re excited to see what he’ll do as a part of Arrow McLaren SP.”
Rosenqvist’s form has improved since his Detroit crash last year forced him to miss two races and scored his best finish with the team since arriving from Chip Ganassi Racing prior to the 2021 season with fourth in last weekend's Indianapolis 500.
Continued form such as this would likely see team owners Brown, Kiel, Sam Schmidt and Ric Peterson content to go into 2023 with an O’Ward-Rosenqvist-Rossi line-up.