Coastal megacities all over the world face challenges related to climate adaptation, ecosystem protection and inclusive development. In response, governments develop high-level and long-term climate adaptation plans to guide coastal development. In Metro Manila, a consortium of Dutch and Philippine consultants developed the Manila Bay Sustainable Development Master Plan (MBSDMP). The planning team stressed the importance of inclusive and participatory planning, yet, the pre-set premises of the masterplan, such as the high-level and long-term planning scale and corresponding problem formulation, determined which justice claims were foregrounded in the project, disadvantaging small-scale fishing and informal settlement communities. ‘Justice’ is a contested concept. Hence, we deploy a critical theory and politics of expert knowledge lens to investigate how struggles over competing justice claims unfold in water development planning. The scalar politics as manifested in the MBSDMP planning process hides particular conceptions of justice while privileging others in congruence with the larger scale uneven political-economic development dynamics. We provide three examples of scale framing in the planning process that functioned to legitimize the contested displacement of informal settlements by pointing to economic development, disaster risk reduction, or environmental protection. Planning design choices involving scalar out-zooming enabled the uptake of these justice claims, while backgrounding the justice claims of negatively affected groups: namely, the urban poor and small-scale fishing communities. The case analysis provides conceptual-empirical insights relevant for coastal cities' grassroots and policy action platforms anticipating climate change impacts and strategizing their stance in the politics of climate adaptation planning.