Between 3 April and 18 May 2007, 21 confirmed cases of measles were reported in members of the Irish traveller ethnic group who attended a funeral in London, England. The Health Protection Agency conducted an investigation to determine the extent of this outbreak in order to inform prevention of future outbreaks. From 23 March to 30 June, 173 outbreak-associated cases from seven regions throughout England were identified; 156 cases were in Irish travellers and 17 were epidemiologically linked to cases in that community. In total, 124 cases were laboratory confirmed (IgM or RNA); none were vaccinated against measles. MMR vaccination was offered on traveller sites. Low vaccination coverage and the movement of traveller communities present particular challenges for measles elimination in Europe. We recommend parallel approaches to improve integration of Irish travellers within routine health services whilst offering targeted interventions to increase vaccine uptake in this marginalized community.