People shape the development of our society and the majority of the world’s population lives in urban areas. Given these circumstances, there is high value in supporting municipalities in their transition towards sustainability. Municipalities have the opportunity to engage directly with the general public by utilizing a participatory approach in planning and decision making. This thesis explores the conditions that enable and hinder municipalities from (i) engaging with the public and (ii) achieving effective and meaningful participation from their citizens. The findings of this study were incorporated into the Ideal Case for Strategic Integrated System Development (SISD), an outline for participatory and cross-sectoral planning towards sustainability in cities and nations. The research focused on developing the elements of engagement and participation in the Ideal Case for SISD, thereby adding depth to the suggested planning process and making it more relevant for engagement and sustainability practitioners.