The expansion of the marine renewable energy (MRE) sector will increase pressure on sea space and existing maritime users which could potentially lead to conflict. Commercial fishing has been identified by many as the industry most likely to be affected by the development of MRE. In order to reduce the risk of spatial conflict and to enable decision-making based on the co-existence of the two sectors, it is important to gain a better understanding of the attitudes of fishermen towards the development of MRE projects in their locality. A survey was designed to provide quantitative information on fishermen's attitudes to marine renewable energy and the perceived impacts and opportunities. Three MRE developments which have been proposed around the island of Ireland (comprising Republic of Ireland and Northern Ireland) were chosen as case study sites in which to carry out the survey. The sites represent offshore wind, wave and tidal energy respectively and are in differing stages of development. In total, 104 complete surveys were conducted with fishermen located at ports in the vicinity of the case study sites. 40% of those surveyed agreed that it is important to develop marine renewable energy in their locality. A further 15% were neutral on this matter. It is encouraging for developers and policy makers that the majority of respondents (70%) were of the opinion that fisheries and MRE projects can co-exist.