DDB had shared the business with JWT, which handled Lipton Ice Tea in the UK. JWT will remain on the roster for Africa, the Middle East and Asia.
It is understood that DDB will adapt creative work for Europe that was originally intended for the US market, where it already handles the account.
The appointment comes at a key time for the tea brand, which has been earmarked for significant investment as a pillar in Unilever's vitality agenda because of its health and antioxidant properties.
With health high on the public agenda and carbonated soft drinks in decline, the brand is viewed at Unilever as well-positioned for growth.
Although it is the 15th-biggest soft drink in the world, Lipton Ice Tea's marketing in the UK has been small-scale to date. It spent £1.5m on advertising in the year to September 2005, according to Nielsen Media Research.