The expansion of offshore renewables in the German EEZ has raised concerns over potential disturbance to marine mammals, in particular the harbour porpoise (Phocoena phocoena). Recent environmental impact assessment studies for offshore wind farms have generally identified noise emission during construction as the most influential disturbance having an impact on harbour porpoise populations (reviewed in Madsen et al. 2006). Specifically, high sound levels during pile driving can cause temporal displacement effects and may even inflict serious physical damage to their sensory system. However, our knowledge about the temporal and spatial scale of such disturbances is limited and current results do not reveal a coherent picture. The construction of the offshore wind farm “BARD Offshore 1” (80 Tripiles, largely without acoustic mitigation measures) offered the opportunity to investigate the temporal and spatial scale of behavioural responses of harbour porpoises to pile driving using passive acoustic monitoring devices (C-PODs).