Objectives: Higher levels of cognitive reserve (CR) are associated with better cognitive function in later life. In contrast, depressive symptoms, anxiety, and rumination are associated with diminished cognitive function. There has been limited research to date examining the influence of CR on the relationship between mood and cognitive function, and results are inconsistent. The aim of this study was to investigate the role CR plays in the relationships between mood, rumination, and cognitive function in later life. Method: Two hundred and thirty-six healthy people aged 60+ completed measures of CR, depression, anxiety, rumination, recall, and verbal fluency. Participants were dichotomised at the median into those with lower and higher levels of CR. Results: CR, mood, and rumination together accounted for between 13% and 15.6% of the variance in scores on the cognitive tasks in the sample as a whole. Mood and rumination explained a significant amount of variance in cognitive test scores in those with lower levels of CR, but not in those with higher levels of CR. Conclusion: The way in which mood and rumination are related to cognitive function differs depending on the individual's level of CR. These results support the view that it is important to continue to build on CR as people move into later life in order to maintain cognitive health.