This paper explores policy change in Swedish coastal and marine conservation, identifying advocacy coalition factors—focusing internal and external events, policy learning, and negotiated agreements—that explain divergent outcomes in disputed national park planning processes. A longitudinal study, covering three decades of three planning processes, indicates that all factors matter. External and internal events, combined with policy learning or negotiated agreements, constituted the main change pathways. We noted that events' influence on learning and agreements was facilitated by policy brokers and mediated through new venues and altered actor strategies. The findings indicated that competing coalitions' policy beliefs influenced the specific routes taken and underlined the centrality of governmental actors to different outcomes. The study illustrates how political conflicts occur and are addressed in environmental governance, generates insights critical to implementing international and national conservation policy, and builds theoretical knowledge of pathways to policy change in disputed policy processes.