The reprieve follows a press release from GM, which initially reported that Universal McCann had won the entire pan-European account, worth £400m across the continent.
The account, which includes Opel, Vauxhall, Saab and Chevrolet, is worth £85m in the UK alone.
Losing it would have been disastrous for Initiative, which lost the £555m Western European media account for FMCG giant Unilever last month.
Chris Shaw, chairman of Universal McCann, confirmed the European win: “We are absolutely delighted to continue working with one of the best clients in the world.
"We have always been at the side of General Motors and will continue to be there going forward.”
The Interpublic agencies beat off competition from Carat for the account.