DLKW picked up the EUR25 million account after a pitch against McCann Erickson, which holds the bulk of GM's business across Europe.
The move is part of GM's practice of asking its agencies to pitch for each Opel marque. Opel is known as Vauxhall in the UK.
There are also pitches going on for the Corsa brand in Europe and for part of the Vectra range, and agencies are competing for the pan-European Opel SUV business.
The Astra win adds to DLKW's pan-European Opel stable. It picked up the £30 million Vectra account in May following a shoot-out against McCann.
Lowe was knocked out at an earlier stage after its ideas failed in research.
Lowe has also seen a migration of much of its UK Vauxhall business to DLKW. DLKW now holds the Corsa, Meriva, Astra and Agila marques as well as the £10 million Vauxhall dealership business, which it scooped from Lowe Broadway earlier this year.
It will launch the Astra convertible and get customers to re-evaluate the Opel brand as a whole. McCann will adapt DLKW's work for local markets in Europe.
McCann has also picked up several briefs over the past few months. It is working on briefs for the Tigra and Zaphira as well as for Opel's range of upscale, performance cars.
Separately, Vauxhall in the UK has commissioned a group of non-advertising people to create advertising for the brand. Called the VX Collective, the group, which includes a DJ, a designer and a film-maker, has created a 30-second film, which will be shown in cinemas and online.
- Comment, page 52.