Background: There are virtually endless occupational hazards for nurses in the workplace, in relation of their place of employment as well as the working hours which may be categorized into physical, social and psychological hazards. The study aimed to identify the relation between working hours and occupational health hazard among staff nurses at hospitals. Research design: A descriptive correlation research design was utilized in this research. Sample: Convenience sample were included all staff nurses who worked in critical care units in the three hospitals (Intensive Care Unit, Dialysis Unit, Neonatal Intensive Care Unit and Emergency Care Unit) with total number is (301) nurse. Setting: This research was conducted at critical care units in three different hospitals named as Minia University, Minia General Hospital, and Alfekrya at Minia governorate, Egypt. Tools of data collection: two tools were used, 1^st tool: Working Hours Questionnaire and 2^nd tool: Occupational Health Hazards Questionnaire. Results: reveals that (91.7%) of the staff nurses were high exposure total hazards, while (8.3%) of them were low exposure total hazards.  Conclusion: There were positive correlations between health hazards and (the number of working hours you work each week as well as the number of overtime hours you work each week).Recommendations: Providing clear and specific job description, flexible work schedules, fair treatment and regular meeting between supervisors and their staff nurses to discuss any occupational hazards and solve their problem