The COVID-19 pandemic caused a global health crisis that affected every aspect of society worldwide. However, the detrimental health effects of the pandemic were not equally distributed across groups and places. Likewise, adherence to preventive measures varied across groups and communities. Having supportive social networks and living in areas with social cohesion—social capital—is believed to protect against adverse consequences of social crises. This mixed method study aims to investigate the bidirectional relationship between social capital and the COVID-19 pandemic, and to analyze the significance of individual and neighborhood social capital for physical and mental health, attitudes toward- and adherence to preventive measures. The specific objectives are to; (1) Investigate the development of neighborhood social capital during the COVID-19 pandemic and to assess whether perceptions on how the pandemic affected life situation and attitudes toward preventive measures differ across neighborhoods with different social capital profiles and population characteristics. (2) Analyze the effects of individual social capital on physical and mental health, as well as attitudes toward and adherence to preventive measures for diverse population sub-groups, living in neighborhoods with different social capital profiles. (3) Analyze how the pandemic and its associated preventive measures impacted people’s access to and utilization of social capital. Sub-study 1 will utilize data from repeated cross-sectional social capital surveys conducted before and after the COVID-19 pandemic, in 2020 and 2024. Data from a cohort who responded to both the post- and the pre-COVID social capital surveys will be linked to population register data on socioeconomic and sociodemographic factors and health registers to be used for the quantitative sub-study 2. A strategic sample of individuals who participated in both the 2020 and the 2024 social capital surveys will be invited to participate in interviews for a subsequent qualitative sub-study 3. This study is carried out in Umeå Municipality, Northern Sweden, where extensive research on social capital, health and social sustainability has been conducted since 2006. The proposed study contributes novel knowledge on how a social crisis affects unequal living conditions between groups and places. This knowledge can provide a basis for what actions are needed to reduce adverse health consequences of social crises.