Aims: The present study set out to investigate the relation of psychological stress to cognitive performance and its interplay with key life course markers of cognitive reserve and social capital in a large sample of older adults. Methods: We assessed cognitive performance (verbal abilities and processing speed) and psychological stress in 2,812 older adults. The Participants reported information on education, occupation, leisure activities, family, and close friends. Results: Greater psychological stress was significantly related to lower performance in verbal abilities and processing speed. Moderation analyses suggested that the relations of psychological stress to cognitive performance were reduced in individuals with higher education, a higher cognitive level of the first profession practiced after education, a larger number of midlife leisure activities, a larger number of significant family members, and a larger number of close friends. Conclusion: Cognitive reserve and social capital accrued in early and midlife may reduce the detrimental influences of psychological stress on cognitive functioning in old age.