Introduction: Research findings suggest that the adjustment of a family is influenced by a mentally- disabled child. Therefore, the current study aimed at investigating the relationship between familial performance, child characteristics, demographic variables and stress and mental health among parents of children with mental disabilities.Method: 200 parents (130 mothers and 70 fathers) were studied; they completed the “parenting stress index”, “General Health Questionnaire”, “FAD-I” and demographic questionnaires for parents and children. Data were analyzed using multi-vitiate Analysis of Variance, correlation and regression analysis.Results: Among child characteristics, child age had a negative relationship with parenting stress and GHQ. Severity of child’s mental disability had a negative relationship with GHQ. The correlation between familial income with parental stress and mental health was negative. The correlations between variables of role, problem solving, emotion expression and mental health and parental stress were negative. Regression analysis showed child characteristics variables, familial performance and demographic variables of parents could predict a significant variance of parental stress and mental health.Conclusion: Familial performance, child characteristics and parental demographic variables correlate with mental health and parental stress and can predict them.