Many shared views of both scholars and practitioners reflect spatial planning as a place-creating process that must be understood from a multi-level perspective. Formal and informal planning modes have variations in planning practices in different countries. In this study, we aimed to evaluate the interaction of formal and informal spatial planning in the frame of the spatial planning system in the Baltic Sea region. We were searching to highlight the involvement possibilities of territorial communities in the spatial planning process around the Baltic Sea region, focusing on coastal areas and their specific features in Latvia, Estonia, the Åland Islands of Finland, and Sweden. Involved experts expressed views based on a pre-developed model to identify how institutionalized formal spatial planning relates with informal interventions. This allowed the development and proposal of a model for coastal area spatial planning and implementation. We concluded that in the spatial planning approach, the governance works differently in different countries, and coastal area spatial planning differs from regular spatial planning. The information base is sufficient to initiate spatial planning at the municipal level, but municipalities should be more active, involving territorial communities in the planning, implementation, and control of municipal spatial planning, as this ensures a greater interest in the use of planning outcome.