<p>The Baltic Sea suffers from excessive input of nutrients leading to eutrophication as a key pressure for the marine ecosystem. Land-based pollution from agricultural activities constitutes a major source of nutrient input to marine environments. To reduce nutrient runoff from agriculture, European and national policymakers have introduced regulations, such as the EU-Nitrates Directive, the HELCOM-Baltic Sea Action Plan, and national fertilizer regulations. However, the effect of these regulations and measures has been limited so far. One reason for this is the limited acceptance of regulations by farmers. By combining theoretical-conceptual literature on individual acceptance with insights from empirical research on agri-environmental schemes (AES) and farmers’ behavior, the paper develops a comprehensive analytical framework for systematically studying central determinants of individual acceptance of agri-environmental policy regulations. A local case study of a nearshore area at the Baltic coast in Northern Germany is conducted, where intensive agricultural production takes place. The paper uses qualitative content analysis of twenty semi-structured qualitative interviews with local farmers as well as political and administrative authorities in the region. Findings indicate that, in particular, economic concerns, policy design factors, and different dimensions of political mistrust – interacting in a wicked-problem complex – cause substantial acceptance deficits. Apart from providing new conceptual insights for multi-disciplinary research on individual acceptance of (marine) environmental protection, the paper also offers insights about how to further develop governance approaches for reducing agricultural nutrient input in marine water, as well as for other land-based sources of marine pollution.</p>