Growing evidence suggests that obesity has negative effects on brain function and structure. Obese individuals exhibit abnormal neural responses in relation to food cues, taste and smell, resting-state activity, and functional connectivity. They also demonstrate impairments in cognitive tasks such as decision-making, inhibitory control, learning and memory, and attention. Bariatric surgery, as a specialized treatment approach, can alter the anatomy and physiological mechanisms of the digestive system, thereby restricting food intake or modifying nutrient absorption to achieve short-term and long-term weight loss effects. It can also improve complications, reduce mortality rates, and enhance quality of life. Recent studies have shown that bariatric surgery has a positive effect on improving obesity-related cognitive dysfunction. This article provides an overview of the association between obesity and cognitive function and focuses on the research progress in recent years regarding the improvement of obesity-related cognitive impairments through bariatric surgery. Several mechanisms may be involved in bariatric surgery to improve obesity-related cognitive dysfunction. Potential mechanisms include weight loss, altered hormone regulation (e.g., ghrelin, leptin), improved insulin sensitivity, reduced systemic inflammation, and changes in gut microbiota. The relationship between bariatric surgery and cognition is complex and multifactorial, and the exact mechanisms are still being explored. Effects of obesity-related complications, hormonal changes, gut-brain-axis, inflammation, brain structure, and nutritional factors on cognitive function after bariatric surgery were discussed. Identifying these mechanisms could help uncover new targets for intervention and provide a basis for optimizing patient outcomes in terms of weight loss and cognitive function.