Nick Heidfeld joined the Mercedes Formula One team as test and reserve driver on Thursday, completing a trio of Germans in a line-up led by Michael Schumacher and Nico Rosberg.
"Whilst I would of course have preferred a seat as an active driver, I am really proud to be part of the new Silver Arrows team. I have seen how committed everyone at the team is and I feel the same," Heidfeld said in a statement.
The 32-year-old, who raced for BMW-Sauber last year, has competed in 167 grands prix without winning any of them. He has finished second on eight occasions, however.
Renault, who have signed his 2009 team mate Robert Kubica, had been Heidfeld's last remaining hope of a competitive race drive but they opted for Russian Vitaly Petrov.
The only other teams with vacancies are newcomers Campos and US F1.
Thursday's announcement brought Heidfeld's Formula One career full circle, with the German starting out as a test driver at Mercedes-powered McLaren in 1998 before making his debut with Prost in 2000.
Seven-times champion Schumacher was tempted out of retirement at the age of 41 after Mercedes bought Brawn, who won both titles last season.
"It's a great pleasure for us to have signed a driver of the calibre and experience of Nick Heidfeld," team principal Ross Brawn said.
"Nick has over 10 years of experience in Formula One working with established teams and he will be a great asset to Mercedes GP. I am confident that his input into the development of our MGP W01 car will be invaluable."