European Researchers' Night is an annual celebration of research and its role in European society. It was first held in 2005 and now takes place in up to 300 locations across Europe with the aim of bringing researchers closer to the general public. European Researchers' Night has benefited from more than €40 million in funding from the European Commission over the last decade. With the prospect of further funding being made available in the coming years it is important to determine if that investment is justified. In Ireland, European Researchers' Night is the only event of its kind that collectively opens the doors of laboratories and research centres so that the public and media can spend an evening engaging with researchers and their work. In this paper we describe our evaluation of European Researchers' Night in Ireland. The evaluation reveals the perceptions of European research among different publics and the strengths and weaknesses of European Researchers' Night as a public engagement event.