Background: Sleep disorders are prevalent complication in patients with end-stage renal disease undergoing hemodialysis (HD). The factors affecting sleep quality (SQ) of patients on HD have not been completely recognized yet. In addition, some studies have shown that poor SQ increases the risk of mortality in patients on HD. Objectives: This study aimed to identify the prevalence of poor SQ and its associated risk factors in Iranian patients on HD. Patients and Methods: This cross-sectional and multicenter study was conducted on 6878 patients on HD from 132 dialysis centers in Iran. Sleep domain of disease specific core of KDCS-SF questionnaire and generic core of this questionnaire (SF-36) were used to assess patients’ SQ and quality of life (QoL), respectively. A poor SQ was defined as a score of ≤ 61.2. Logistic and linear regression analyses were applied to assess predictors of SQ and their associations. Results: The mean age of patients was 54.4 ± 17.1 years and 39.7% of patients were > 60 years old. The majority of our patients had poor SQ (60.6%). Patients with diabetes mellitus were significantly more likely to have poor quality of sleep (63.4%). In logistic regression analysis, there were significant correlation between good SQ and younger age, shorter dialysis vintage, less muscle cramp, high QoL, high cognitive function score, and high sexual function. In addition, linear regression showed a significant association among SQ, QoL, and hospital stay as an outcome. Conclusions: With improving some factors and QoL of patients on HD, we can promote SQ in these patients that it might lead to reduction in length of hospital stay.