The team said on Monday that the former DTM (German touring car) champion, who will continue to race in that series with a Mercedes team, was leaving after eight years as a tester and hundreds of hours in the simulator.
"I've loved working for McLaren and hope my feedback and input over the years has been beneficial," the 33-year-old said in a team statement.
"The engineers I've worked with have been kind enough to say that it has. I have many friends at McLaren, and I wish all of them the very best of luck for the future."
McLaren have yet to confirm their 2015 driver lineup, with Spaniard Fernando Alonso expected to return to the team from Ferrari.
(Reporting by Alan Baldwin, editing by Stephen Wood)
