The foreseen, and already ongoing, substantial increase in offshore renewable energy and corresponding infrastructures urges policymakers and scholars to carefully consider corresponding long-term environmental effects on the marine environment. Strategic Environmental Assessment (SEA) is becoming a standard tool for Marine Spatial Planning (MSP) processes for enabling planners to develop more sustainable marine spatial plans. To explore how SEA can contribute to a more strategic and environmentally-oriented MSP practice, four SEA processes from four North Sea countries are examined, building on available SEA documents and semi-structured interviews. The results show that SEAs for MSP can take an exploratory or appraisal-oriented approach. Adopting an exploratory approach can open up comparatively more opportunities for SEA to contribute to MSP than an adopting an appraisal-oriented approach, but it requires an early initiation of the SEA within the larger planning process. Still, it does not imply that there is one single best method. Rather, the institutional context establishes the conditions for SEA processes to contribute to MSP practice. Particularly, the political pressures and prior sectoral policymaking for offshore renewable energy restrict what can be included in the scope of an SEA. Also, the limited knowledge on the larger dynamics of the marine environment complicate the assessment of transboundary and cumulative effects. Therefore, as future research continues working towards a robust scientific knowledge base on the marine environment, it is crucial that scholars and policymakers collaborate on a structural basis to bridge the gap between science and policy implementation.