High adiposity in middle age is associated with higher dementia risk. The association between weight loss and cognitive function in older adults is still controversial. A meta‐analysis was undertaken to estimate the effectiveness of intentional weight loss on cognitive function in overweight and obese adults. A structured strategy was used to search randomized and non‐randomized studies reporting the effect of intentional and significant weight loss on cognitive function in overweight and obese subjects. Information on study design, age, nutritional status, weight‐loss strategy, weight lost and cognitive testing was extracted. A random‐effect meta‐analysis was conducted to obtain summary effect estimates for memory and attention–executive domains. Twelve studies met inclusion criteria. Seven were randomized trials and the remaining five included a control group. A low‐order significant effect was found for an improvement in cognitive performance with weight loss in memory (effect size 0.13, 95% CI 0.00–0.26, P = 0.04) and attention/executive functioning (effect size 0.14, 95% CI 0.01–0.27, P < 0.001). Studies were heterogeneous in study design, sample selection, weight‐loss intervention and assessment of cognitive function. Weight loss appears to be associated with low‐order improvements in executive/attention functioning and memory in obese but not in overweight individuals.