Aim and Background: Health, including mental health nurses, considering effective nurses role in health system as providers of care in improvement of patients´ quality of care, have a crucial importance. Further studies on the relationship between demographic variables and mental health are still conflicting results. Hence, the present study was carried out to predictors of nurse's mental health in medical and surgical wards based on demographic variables.Methods and Materials: This was a descriptive correlation study that was implemented in 380 nurses in hospitals affiliated to Isfahan University of Medical Sciences were randomly chosen. Data gathering tool included demographic information and General Health Questionnaire (GHQ-28). The data was analyzed by descriptive and analytical statistics (Student t-Test, one way ANOVA and Multiple linear regressions), with applying SPSS 20 software.Findings: In terms of nurses´ general health, 69.73% (n=265) had scores greater than 23 suspected to have physical or psychological disorders. Based on the findings of this study, there was not a significant correlation between mental health of nurses with age, marital status, sex and nurses' number children. While there was a significant relationship between sleep quality, overtime worked and work history with nurses’ mental health. The results of regression analysis indicated that the sleep quality, overtime worked and work history explained totally 40.9% of the variance of nurses' mental health. (R2=40.9).Conclusions: According to the research, more than half of the nurses in the study were suspected mental health problems, and nearly two-thirds of the mental health nurses were somewhat desirable or undesirable. It is suggested that managers of health services operate the measures to improve workplace conditions and mental health nurses. Based on the present study results, level of mental health is predicable according to some demographic variables in regression model.