Impairment of cognitive functions occurs frequently in chronic kidney disease (CKD). The conditions most associated with this decline are depression, delirium, mild cognitive impairment and dementia. The mechanisms involved have not been established yet, but some factors, as neuronal damage by uremic toxins, cerebrovascular ischemic lesions, oxidative stress, chronic inflammation, anemia, hyperhomocysteinemia, the endothelial dysfunction may play a critical role. The neuropsychological performance improves with the initiation of dialysis, although some cognitive dysfunctions remain even after treatment, especially in the areas of attention, cognitive flexibility, memory and learning. Kidney transplantation may improve and even reverse some cognitive deficits detected in the dialysis period, despite some compromise in verbal memory and executive functions remain after transplantation. The diagnosis of cognitive decline in patients with CKD may have an important impact on the management and prognosis. This paper presents an update on the decline of cognitive function in patients with CKD.