In this chapter, we review how developers complied with the environmental license conditions formulated to mitigate the potential negative impacts of pile driving on marine mammals in the Belgian part of the North Sea (BPNS), whether this impacted the timing of development and what the likely consequences were for marine mammals. Between 2009 and 2020, offshore wind farm developers in the BPNS complied to a large extent with those environmental license conditions formulated to mitigate the potential negative impacts of pile driving on marine mammals. However, we did identify several possible improvements to these environmental license conditions, including changes in the use of acoustic deterrent devices, formalising obligatory mammal surveys, and requiring developers to comply with the national threshold for impulsive underwater sound. The reduction in the costs of applying noise mitigation measures ensures that these suggested improvements should not affect the economic viability of future projects.