Demography (also referred to as population studies) is the study of the size, distribution, and composition of a population. Three processes influence population change over time: fertility, mortality, and migration. In recent decades, the scope of population research has expanded dramatically, applying a demographic lens to policy-relevant topics like education, employment, poverty, health, crime, and residential segregation. While demographic research may sound technical and mechanistic, nearly every phenomenon studied by population scientists both shapes and is shaped by complex social psychological processes. We first define the core concepts used in population studies and provide examples of how these outcomes are both influenced by and influence social psychological processes. We highlight three contemporary topics in social demography: family diversity, mortality disparities, and informal caregiving. Our discussion is motivated by the social structure and personality framework, which delineates how macro- and meso-level forces bear on micro-level outcomes. We argue that an understanding of demographic phenomena necessitates an infusion of ideas and concepts from social psychology, including stress and coping, reference group, stigma, and cultural script theories. We conclude by suggesting one critical area for collaborative research by demographers and social psychologists: the macro-, meso- and micro-level impacts of climate change.