Although intolerance of uncertainty (IU) is associated with negative outcomes, studies focusing on older adults are still emerging. Specifically, the relationship between IU and psychological health in this population remains unclear. Moreover, no review has focused on understanding the unique contributions of IU and aging to anxiety and mental health in older adults. This scoping review and meta-analysis addressed this gap and provided a comprehensive understanding of the relationship between IU, aging, and mental health. Among 45 studies reviewed, 37 were included in the meta-analysis using mixed effect analysis to examine the relationship between IU and age across adulthood. The remaining eight studies, along with seven selected from the meta-analysis, were included in the scoping review to evaluate the relationship between IU, anxiety, and mental health. Among these, 12 studies focused on late adulthood, two on overall adulthood, and one included both late and overall adulthood. Results of the meta-analysis revealed an overall significant age difference in IU throughout adulthood. Moreover, results of the scoping review indicated a direct correlation between IU and anxiety, and other psychological issues in elderly. These findings provide insights for future research and interventions aimed at reducing IU and improving mental health among older adults.