Cities around the world constitute complex systems, as sets of sub-components that are connected and interact with each other. Due to this inherent complexity, there are numerous emerging challenges that need to be tackled. In those complex environments, various-interest groups collaborate and compete to achieve their goals and interests, constituting a vital part of urban planning. The advancement of technology and ICT, and the abiding need to keep citizens engaged, marked a critical shift in the way that urban planning confronts the increasingly contemporary complex issues. This advancement has offered citizens a way to digitally participate in urban planning procedures, overcoming certain limitations, while posing, also, challenges related to the level of its effectiveness. While many methods and tools have been developed over the years, for enhancing citizen engagement and the effectiveness of public participation, there seems to be an evident gap in substantial and two-way collaboration among the (relevant) urban stakeholders. This thesis project aims to hark the perspectives and needs of the urban stakeholders, translating them into a conceptual design of a digital public participation platform. Next to that, except for the importance of the platform itself, as a tool, the focus was also given to participation, as a process, considering that such a platform could and should act as a promoter of effective public participation rather than a stand-alone solution. Consequently, the main research question of this study is: Which characteristics need to be included in designing a public participation platform so that it can enhance citizen engagement and facilitate more effective public participation in urban planning? For this research, a design science research approach was chosen. A theoretical background was developed on existing theories, methods and frameworks related to public participation and digital platforms. Data collection was conducted using multiple methods, including workshops, semi-structured interviews, and questionnaires, while data analysis was conducted inductively, to identify all the emerging patterns and their interrelations. From the data analysis, five core themes emerged: General findings; (De)Motivational factors for public participation; Characteristics; Technical requirements; Technological features. Retaining these themes, the analyzed results were then critically synthesized, both in qualitative and quantitative terms, to provide a holistic overview. Combing the obtained results, the main research outputs were developed, providing an overall answer to the main research question. First, a trifold validation of the results, related to the past, present, and future, was conducted, fulfilling the rigor and design cycle of the design science research, and attaining a continuous assessment. Building upon the evaluation results, for the platform as a tool, a conceptual design was developed, based on the different views of the urban stakeholders. For the process of public participation in general, a set of guidelines was developed, providing recommendations on how to enhance citizen engagement and the effectiveness of public participation, based on the different views of the urban stakeholders. This thesis concludes with some important final remarks, including limitations, recommendations for future research, research relevance, and the author’s final reflections on the research.