Offshore wind has the potential of becoming an important pillar of the future European energy system. It can contribute to policy objectives on climate change, energy security, green growth and social progress. However, the large potential of offshore wind does not automatically lead to a large share in future energy systems; neither does the emergent stage of development of the technology. Recent insights in innovation studies suggest that the success chances of technological innovations are, to a large extent, determined by how the surrounding system - the innovation system - is built up and how it functions. In this paper we assess the offshore wind innovation systems of four countries: Denmark, the UK, the Netherlands and Germany with the objective to provide recommendations for strengthening the overall European offshore wind innovation system. We use the Technological Innovation System (TIS) approach to analyse the system in 2011. Based on the analysis we identify a number of challenges that the European offshore wind sector faces. Some of them include: a serious deficiency of engineers; fragmented policies and poor alignment of national regulatory frameworks; cost of the technology and limited grid infrastructure. Since the problems hinder the entire system development we call for a systemic policy instrument that would support the innovation system around this technology and contribute to its wider diffusion in Europe. © 2013 Elsevier Ltd.