Chronic kidney disease (CKD) is increasingly recognized not only as a kidney disorder but also as a contributor to cognitive impairment (CI). The kidney and brain share a common vulnerability to uremic toxins, whose accumulation in CKD is exacerbated by gut dysbiosis. These toxins impair the integrity of the blood-brain barrier (BBB), reduce neurogenesis, and promote neuroinflammation. Therefore, maintaining brain health in CKD requires a holistic approach targeting the gut–kidney–brain axis. Nutritional strategies, particularly plant-based diets such as the Mediterranean or dietary approaches to stop hypertension (DASH) diets, have demonstrated benefits for both renal and cerebral outcomes.