Many regions throughout the world that are suitable for exploitation of the wave energy resource also experience large tidal ranges and associated strong tidal flows. However, tidal effects are not included in the majority of modelling studies which quantify the wave energy resource. This research attempts to quantify the impact of tides on the wave energy resource of the northwest European shelf seas, a region with a significant wave energy resource, and where many wave energy projects are under development. Results of analysis based on linear wave theory, and the application of a non-linear coupled wave-tide model (SWAN–ROMS), suggest that the impact of tides is significant, and can exceed 10% in some regions of strong tidal currents (e.g. headlands). Results also show that the effect of tidal currents on the wave resource is much greater than the contribution of variations in tidal water depth, and that regions which experience lower wave energy (and hence shorter wave periods) are more affected by tides than high wave energy regions. While this research provides general guidelines on the scale of the impact in regions of strong tidal flow, high resolution site-specific coupled wave-tide models are necessary for more detailed analysis.