Aims: The present study set out to investigate the relation of obesity to performance in verbal abilities, processing speed, and cognitive flexibility and its interplay with key correlates of cognitive reserve in a large sample of older adults. Methods: A total of 2,812 older adults served as a sample for the present study. Psychometric tests on verbal abilities, processing speed, and cognitive flexibility were administered. In addition, individuals were interviewed on their weight and height (to calculate body mass index; BMI), educational attainment, occupation, and engaging in different activities throughout adulthood. Results: Obesity (BMI ≥30) was significantly associated with a lower performance in verbal abilities, processing speed, and cognitive flexibility. Moderation analyses showed that obesity was related to lower processing speed and cognitive flexibility only in individuals with low engagement in activities and low education. Hierarchical regression analyses showed that obesity was not related to any of the three investigated cognitive performance measures when cognitive reserve in early and midlife was taken into account. Conclusion: Present data suggest that cognitive reserve accumulated during the life course may reduce the detrimental influences of obesity on cognitive functioning in old age.