The present study was a cross-sectional investigation carried out on elderly patients under chronic hemodialysis who referred to Firoozabadi Hospital during 2019-2020. The study population was 80 patients ≥ 60 years. The patients' cognitive status was determined using MMSE and MOCA tools. The mean age of the candidate patients was 71.71 ± 6.28 years old. Cognitive function was assessed by MMSE and MoCA tests and the mean score of the MMSE test was 20.05 ± 3.50 with the highest score being 26 and the lowest score being 12. Based on the results, these patients were divided into three groups with normal cognitive function, mild cognitive impairment, and severe cognitive impairment. According to the results of the MMSE test, 19 patients (23.75%) had a normal cognitive function and 45 patients (56.25%) had impairment.In other words, the older patients, the lower level of education, the longer duration of hemodialysis, and the patients with a history of diabetes were more susceptible to cognitive impairment. Subsequently, there was a positive correlation between the levels of BUN, creatinine, uric acid, and PTH, which means that the higher level of these variables in patients was related to the higher risk of cognitive impairment. The findings of the present investigation revealed that the cognitive function and the studied variables including age, level of education, history of diabetes, hemodialysis duration, BUN, Creatinine, Uric Acid, PTH, Sodium, and Kt/V had a significant difference in patients undergoing hemodialysis.