Policy change is often described as a consequence of different types of perturbations. The advocacy coalition framework (ACF) on the other hand advocates that policy changes are accomplished by changes among involved actors’ beliefs and behavior. The Baltic Sea Action Plan (BSAP) with its so called ecosystem approach, signed by the countries surrounding the Baltic Sea and the European Community in 2007, is such a policy change. Yet, the causes behind the launch of the BSAP are unknown. By studying involved actors’ beliefs and behavior this study shows that the BSAP was caused by a general shift in beliefs among all involved actors rather than by competing beliefs or changed actor behavior. The changed beliefs among the actors is either caused by learning processes or negotiations, however the relationship between these two remains unexplored. No coordinated behavior among the actors could be identified during the analyzed period.