We propose to examine the COVID-19 pandemic as a natural experiment to investigate how social experiences are associated with trajectories of change in physical activity and psychological well-being in adults 55 years and older. We also propose to examine how older adults’ social experiences, physical activity, and well-being changed over time during the COVID-19 pandemic. 890 participants reported social, physical activity, and psychological well-being experiences by completing six surveys approximately every four weeks. Latent growth curve models will (1) examine the trajectories of change of social experiences, physical activity, and psychological well-being, (2) examine the degree to which baseline reports of social experiences are associated with physical activity, positive affect, negative affect, and perceived stress trajectories over time, and (3) examine how trajectories of change in social experiences are associated with trajectories of physical activity, positive affect, negative affect, and perceived stress trajectories over time. Findings will contribute to further clarifying associations among social experiences, physical activity, and psychological well-being, as well as assist with informing adherence strategies needed to increase physical activity participation and maintenance among aging populations.