Social media have been increasingly used by governments and planning professionals to gain public opinions, distribute information, and support participation in planning practices. Nevertheless, few studies have been conducted to understand the influence of local contexts and the extent to which social media can enhance citizen power and inclusion. This study investigates the role of social media in citizen participation by taking case studies in the Netherlands. It adopts a mixed methods approach that combines interviews, web scraping, and content analysis to understand the characteristics of social media participation. There are several key findings. First, support policies and a high level of social media penetration rate are preconditions for more inclusive participation. Second, social media enhance social inclusion by engaging many participants, who may not be able to participate via traditional methods. Third, they facilitate interactions and different levels of citizen power, though the government still plays a leading role within top-down approaches. Finally, they improve the effectiveness of participation regarding transparency, accessibility, and workable solutions. However, there are several potential political and social bias associated with social media technology. The combination of online and offline participation methods is properly necessary to engage different groups in the planning process.