McLaughlin leaves the Supercars arena ranked fourth on the all-time wins list with 56 career victories, and second on the all-time list with 76 career poles in just eight full seasons of racing.
"It's a sad moment for a lot of us – it's been a wild ride," McLaughlin said.
"To venture to the other side of the world and into a car and a series I don't know, it's something that has been difficult, but it's made easier when you have good people around you and supporting you.
"I'm so excited for the opportunity to take the next step in my career and compete against some of the best drivers in the world in the Indycar series.
"The last four years racing for DJR Team Penske has been amazing. I want to thank every single person on the team, and everyone that has helped me reach this point in my career.
"I wouldn't be in position to continue to chase my dream without the hard work of so many people along the way. I'm looking forward to the challenge of joining one of the most iconic motorsports programs of all time – Team Penske's IndyCar team. I wish the 2021 season would begin tomorrow."
McLaughlin will join former Indycar series champions Josef Newgarden, Will Power and Simon Pagenaud in Team Penske's 2021 Indycar lineup, with the 2021 season beginning in March.
Team Penske founder and CEO Roger Penske says it's been a tough decision to pull out of a series it has been so successful in.
"We have enjoyed an incredible six seasons competing in the Supercars series with DJR Team Penske," said Penske.
"Unfortunately, with the challenges we have faced in 2020 as a result of the Covid-19 pandemic, we have had to readjust our business initiatives for 2021 and beyond."
Fans of Dick Johnson Racing can breathe easy, as the Supercars legend has confirmed his team will live on.
"While we hate to see them go, we understand the tough business decisions that have to be made. We've worked together over the last six years to build a team that has become the benchmark for performance both on and off the track," said Johnson.
"With the assistance of Roger and Team Penske we will be in position to build on that success. Our team will continue to be a leader in Supercars racing."
And, McLaughlin could be back in the Supercars fold before long – at least in one race.
"I'm sure I'll be back for Bathurst, if someone wants me as a co-driver, I'd certainly love that."