ABSTRACT Hemodialysis (HD) is a common treatment for Chronic Kidney Disease (CKD). Objective: the objective of the present study was twofold. First, to assess the level of physical activity and cognitive function in hemodialysis (HD) patients and, second, to compare cognitive function of active and insufficiently active HD patients. Methods: the sample consisted of 84 HD patients. Data collection took place in two different Renal Replacement Therapy Units (RRTU) in Brazil. A sociodemographic and clinical structured interview, the International Physical Activity Questionnaire (IPAQ) and the Addenbrooke's Cognitive Examination Revised (ACE-R) were used for data collection. The Mann Whitney U-test was used to compare cognitive function between groups. The significance level adopted was p≤.05. Results: the majority of the patients were insufficiently active. The total average score on the cognitive test was lower than recommended and physically active HD patients had a significant score in the fluency domain. Conclusion: we found that HD patients are at greater risk of developing cognitive deficits. Physical activity was shown to be a potential non-pharmacological, low-cost therapeutic alternative for improving cognitive abilities in HD patients. The present study can help health professionals to encourage HD patients to engage in regular physical activity and contributes to the development of specific protocols for these patients.