The appointment follows a pitch against roster agencies, and comes ahead of the launch of its "ecoFlex" car technology, which will be unveiled this week at the Frankfurt Motor Show.
DLKW will create a pan-European advertising campaign raising awareness of the environmental merits of the technology. Media plans are still being finalised, but are likely to include television, press, outdoor and digital media. The pitch was managed by GM Europe out of its Frankfurt office.
The ecoFlex technology emits lower CO2 levels and consumes less fuel. It will debut on the Vauxhall Corsa 1.3, with plans to roll it out across all models and engines in its range over the next five years.
DLKW works primarily on GM's Vauxhall Corsa and Astra lines, but created a specialist environmental ad - "scrap your banger" - this summer that encouraged drivers to trade in their old cars in exchange for Vauxhall's lower emission models.
GM is also developing hydrogen fuel cell cars, which will have zero-emissions, and has invested $1 billion in the US into the initiative.