D'Arcy beat AMV, WCRS and BMP DDB to the £2 million account.
The DoT - formerly called the Department of Transport, Local Government and the Regions - put the business up for pitch in May after breaking away from COI and appointing its own roster of agencies. Tony Allsworth, the head of transport publicity, said the review was about finding the best creative work and said D'Arcy's had performed the best in research.
"The impact of these ads is crucial, with many in the past having an 80 per cent to 90 per cent awareness among the public, he said.
"D'Arcy's work showed a real insight into the way our core target audience thinks and feels about drinking and driving. The idea, in research, was able to tap into the audience's perceptions and make them think about their own drink driving behaviour."
AMV's work was weighted toward the Christmas period but the DoT is briefing D'Arcy to develop work that can run throughout the year.
Allsworth said D'Arcy was working on its first campaign - a TV ad which will break in October - and added that any new work would include through-the-line executions. The media account, handled by Carat, is unaffected.
D'Arcy's managing director, Barry Cook, said: "We are very proud to have this respected and prestigious account back. However, what really matters is that our work makes a difference."
D'Arcy created the award-winning "Dave TV campaign, which featured a man disabled after a drink drive car accident. It first won the account as DMB&B in 1991 and worked on it until 1998, when AMV won a creative review of the business.