This article deepens our understanding of the preconditions for policy-oriented learning in conflictive marine conservation, provides an analytical framework for further studies and formulates recommendations for practitioners on what to consider when establishing protected areas. Our seas are under increasing pressure but lag behind in protection. Climate change, intensifying use and biodiversity loss challenge current practises and imply trade-offs between conservation and use. While nature conservation ranks high internationally, national protection attempts often result in controversies, with actors aligning in opposing advocacy coalitions-for and against the proposals. Policy-oriented learning is one way to overcome controversies. It involves processes whereby actors gain new knowledge and experiences, leading to changed beliefs about the problems and possible solutions. We aimed to explore and explain policy-oriented learning through a comparative longitudinal case study of two Swedish national park planning processes with different outcomes: Koster Sea national park, established 2009, and Sankt Anna archipelago remaining without park. Which characteristics related to context, actors and processes influence policy-oriented learning in conflictive marine conservation processes? The results suggest that a set of complementary factors explain the different outcomes. First, learning is facilitated by contexts where actors from both coalitions depend on the resource and its protection and have experience of collaboration, and where conservation planning is well integrated with other governance processes. Second, engaged key actors with moderate views facilitating interactions and able to identify common interests and deescalate conflicts are important - supported, third, by various forums allowing exchange of knowledge and learning across coalitions.