Densification, the increase of built environment elements in urban areas, has been identified as a tool to mitigate social and environmental consequences of urban sprawl, i.e. the continuous extension of urban boundaries and dispersed construction of built-up areas. At the same time, unique environmental and social challenges are requiring urban developers to adapt their approaches to changed long-term or short-term physical conditions while considering the social consequences. Many cities around the globe, and amongst them Amsterdam, The Netherlands, are striving to align urban interventions in the field of densification and climate action. This led to the research question: Which social impacts arise from simultaneous urban densification and climate action in the form of climate change adaptation and the energy transition? This study provides insight into the current knowledge in scientific literature and the perceptions of urban policymakers. A qualitative mixed methods approach was applied. The approach was constituted of a systematic literature review and semi-structured interviews. A social impact framework was combined with an understanding of the natural sciences, engineering and urban planning to assess the social impacts of urban densification in times of climate action. I first collected the current literature at the interface of urban densification, the energy transition and climate change adaptation to compile the perspective of academic literature in a knowledge base. Secondly, I conducted semi-structured interviews with urban policymakers of the Dutch capital of Amsterdam to gain insight into the perspective of policymakers. In the analysis of both my data sets, I discerned explicitly mentioned social impacts as well as social impacts which were not explicitly stated, but could be reasoned from the collected literature and the conducted interviews. Finally, the comparison of both perspectives shows a strong prevalence of social impacts in the spheres of livability in the built environment, health and economic relations. How densification, the energy transition and climate change adaptation exert consequences on communities and institutional relations is much less observed at the current state. Lastly, impacts on cultural or gender relations are close to absent from the discussion - in academic literature and the perceptions of urban policy-makers in the case study alike. While the results are largely connected to the conceptualisation and methods applied, implications can be drawn for future research and policy-making. It is essential to explore the origins of the low occurrence of cultural and gender impacts in the data set to evaluate whether these are due to knowledge constraints or actual low impact rates. But, given the understandings gained, I urge to observe these spheres more strongly, in particular in relation to indirect social impacts. Moreover, the case study shows that social impacts of densification and climate action transitions are highly context-driven. They are subject to questions of ownership, human behaviour, urban inequalities and social differentiation within the constraints of physical space and monetary as well as environmental budgets. Additionally, it is indispensable to further strengthen the interaction and communication between researchers, policy-makers and other stakeholders.