Objectives: The main objective was to determine the efficacy of Mindfulness-Based Interventions in improving the cognitive function of older adults (healthy adults or adults with mild cognitive impairment). Methods: A search was conducted in 4 databases. The effect sizes were extracted to perform a meta-analysis of the cognitive functions, as well as subgroup meta-analyses according to each domain: attention, memory and executive function. Results: The meta-analysis of cognitive functions showed an average effect size of g = .07, 95% CI [-.013; .160], p = .09, with the following values for each domain: g = .02, 95% CI [-.167; .204] for attention; g = .06, 95% CI [-.148; .262] for memory; and g = .14, 95% CI [-.042; .329] for executive function. Conclusion: The MBI had a null global effect. The attention and memory results showed a null effect size and a small effect size was found for executive function. The methodological quality of the studies, however, was poor, so the results need to be interpreted with caution.