Aim: To examine the nature and prevalence of Cambodian nurses' work hours and overtime and related factors Background: The chronic shortage of nursing workforce is a major cause of overtime among nurses. Introduction: Nursing shortage and working overtime among nurses negatively affect nurse and patient outcomes, but nurses' work hours and overtime in Cambodia have not been comprehensively examined. Methods: A multicenter cross-sectional study was conducted in four Cambodian hospitals. Data were collected from 253 nurses providing direct nursing care using a questionnaire. The STROBE checklist was used for reporting this study. Results: More than a fifth of staff nurses worked more than 48 h, which is the legal work hour limit in Cambodia. Two major reasons for working mandatory or voluntary overtime, on-call or 24-h on-call were (a) not wanting to let down colleagues and (b) able to get all work done. The number of patients cared for was related to whether or not nurses worked 48 h or more. Conclusion: Overtime work and adverse nurse scheduling are common in Cambodia. Implications for nursing and health policy: Nurse managers and healthcare institutes in Cambodia need to monitor Cambodian nurses' work hours, which are often beyond the legal work hour limit. Moreover, it is important to understand why nurses work overtime and develop health policies, strategies, and programs that can help promote patient and nurse safety and retain qualified nursing staff. The 24-h on-call practice needs to be regulated according to the labor policy in healthcare institutes to prevent adverse nurse and patient outcomes.