This dissertation analyzes community engagement practices as a fundamental feature of democracy, planning, and policymaking processes. Multiple disciplines, including public policy, planning, and public health, understand community engagement as a mechanism to make planning, policymaking, and research processes and their outcomes more democratic, effective, and sustainable. Yet scholars, practitioners, and community residents continue to observe and experience difficulty collaborating in the design and implementation of policy. I investigated these conundrums of democracy, representation, governance, and collaboration through this dissertation, a four-year ethnographic study of community engagement in a foundation-funded neighborhood health initiative in Southern California.In this dissertation research, I inductively expand current understandings of exclusion and inclusion in planning and policymaking by enlisting practice theory as a theoretical and analytical lens. Practice theory entails both agency and structure; thus, it provides an alternative view to social phenomena, like community engagement, that are commonly studied using an agentic focus (e.g. practitioners need more training to be inclusive) or a structural analysis (e.g. practitioners have the decision-making power and thus exclusion persists). Using a practice lens, I define exclusion through a set of exclusionary practices, all of which prevent connections between different stakeholders, between their issues, and between current and preexisting advocacy and community organizing efforts. I also relate exclusion and inclusion to structural advantages and disadvantages, including the use and maintenance of common organizational and institutional practices in community settings. I describe structural advantages and disadvantages as practices that constitute community power dynamics. Specifically, I explain the relationship between power, defined as the ability to take action, and practices of exclusion and inclusion. I explore the rationale and implications of exclusionary and inclusionary practices by drawing from scholarship on institutional logics. I conclude that community engagement and planning and policymaking are ontologically nonlinear and emergent processes, and that empirical or practical approaches to community engagement must embrace nonlinearity and emergence in order to be inclusive.