Unprecedented global challenges demand wide-reaching societal modification to ensure life support functions and human well-being. In the absence of adequate international responses to climate change and the need for place-based adaptation, local governments have a pivotal role in fostering sustainability transitions. In this context, the importance of ecosystem-based adaptation is increasingly recognized as a multi-benefit approach that utilizes ecosystem services to harmonize human-environment systems. Although research advocates the mainstreaming of ecosystem-based adaptation to advance sustainable planning, the pathways for its systematic implementation are missing and it remains unclear how local authorities can best integrate this new approach into their core work. The purpose of this study is to increase knowledge of the potential ways to mainstream ecosystem-based adaptation into municipal planning. We investigate four coastal municipalities in southern Sweden (Malmö, Helsingborg, Lomma and Kristianstad) and examine, based on vertical and horizontal integration processes, the key characteristics of existing mainstreaming strategies. Results show that, although ecosystem service planning and climate change adaptation planning together establish the conceptual foundation for ecosystem-based adaptation, related activities are often implemented separately and are rarely comprehensive. We illustrate how combined mainstreaming strategies can reinforce and complement each other and how strong leadership in the integration of processes has the ability to compensate for a lack of guidance or supporting legislation from higher decision-making levels. Finally, we conclude that systemic mainstreaming of sustainability issues is a promising avenue for initiating and promoting sustainability transitions and has the potential to address the criticism that other mainstreaming topics have faced. On this basis, we specify the core characteristics necessary to ensure its effective and meaningful application.