The 2022 Indianapolis 500 winner will count Colton Herta and Kyle Kirkwood as team-mates next year, although there has been no word yet on its other incumbents, namely Romain Grosjean and Devlin DeFrancesco.
In fact, aside from the Ericsson deal itself, there are no clues over who he will displace, with a car number and sponsor(s) yet to be announced.
“I'm very happy and proud to be joining Andretti Autosport next season,” said the Swede.
“Andretti is one of the most legendary names in motorsports, so it is definitely a dream come true for me to join this team.
“I want to thank Michael [Andretti] and Dan [Towriss, co-owners] for putting their trust in me, and I can't wait to get to know everyone in the organisation.
“It's a very exciting new chapter in my career, and I'm really looking forward to getting to work achieving our goals together.
“Exciting times are ahead, and I'm thankful for this opportunity.”
Michael Andretti, CEO of his eponymous team, remarked, “Like everyone else, we have paid close attention to Marcus' success in the NTT IndyCar Series and have been impressed with how quickly he proved that he belonged with the frontrunners in what is arguably the most competitive IndyCar field ever.
“It's no secret that we want to win races and championships and to do that we need drivers like Marcus, who have that natural talent and determined drive.
“We are excited for the winning mindset that Marcus brings to the table, and I'm eager to see what next season has in store for us.”
Ericsson has driven for CGR for the past four years, including the present season, challenging for the title last year and falling a lap short of back-to-back Indy 500 wins in this year's controversial finish.
However, the 32-year-old has grown increasingly frustrated at his status as a pay driver within Chip Ganassi's four-car squad, with which he now has just three races left.
A statement from CGR read, “Chip Ganassi Racing wishes Marcus Ericsson all the best in his future endeavors.
“In his time with CGR, the No. 8 team secured four victories, notably the 106th Running of the Indianapolis 500.
“Chip Ganassi Racing looks forward to finishing the year strong and remains dedicated to upholding our winning tradition.
“The team will announce driver updates in due course.”
CGR currently fields Ericsson alongside runaway series leader and 2021 IndyCar champion Alex Palou, six-time champion Scott Dixon, and a #11 entry filled on ovals by two-time Indy 500 winner Takuma Sato and elsewhere by rookie Marcus Armstrong.
It may be that all four of those drivers stay on next year, including Palou, who is now embroiled in a legal dispute over McLaren after it claimed to have him under contract for the 2014 IndyCar Series season.