Aim: Many mothers of children with developmental disabilities are known to experience high levels of stress, and compromised mental health. Research is crucial to better understand and assist mothers with compromised mental health, and ultimately better service families raising and supporting a child with a disability. Method: Data were collected using cross sectional mail-out survey with follow up phone call. Instruments included the Short Form 36 version 2 (SF-36v2) and instruments that measured maternal, child and environmental factors. Descriptive statistics examined characteristics of participants. Correlation, t-tests, and multiple regression analyses were used to identify factors associated with mothers' mental health. Results: Mothers (N = 152) cared for a school-aged child (aged 5-18 years) with high care needs and developmental disabilities including autism spectrum disorder (n = 94); cerebral palsy (n = 29); attention deficit hyperactivity disorder (n = 19). Factors associated with maternal mental health included the child's psychosocial health (r = 0.36) and challenging behaviour (r = -0.33); maternal empowerment (r = 0.40); maternal participation in health promoting activities (r = 0.43); and the child's unmet service needs (r = -0.29). The strongest predictors of maternal mental health in this cross sectional study were maternal participation in healthy activity and empowerment, the child's emotional functioning and unmet service needs. Conclusion: This study identified maternal factors as the most important influence on self reported mental health among this sample of mothers. Findings suggest that service changes that provide mothers with information about their own health and need for health enhancing activities, as well as education that empowers mothers to manage and master their child's disability and needs, may contribute to maternal mental health and well being. (Contains 4 tables.)