The agency triumphed over Dare and Profero in a pitch run by COI Communications.
Agency.com will handle all online advertising for the project, set to launch in February. Media planning and buying will be by i-level.
The Drivers Re-engineering Project will enable people to apply for their driving licences - and keep their details up to date - via the Government's public services website, www.direct.gov.uk.
Agency.com has been briefed to drive traffic to the site and build awareness of the new online services.
The project should cost £35 million and take two-and-a-half years to complete as part of a programme to put government services online.