COVID-19 not only threatens people's physical health, but also creates disruption in work and social relationships. Parents may even experience additional strain resulting from childcare responsibilities. A total of 129 parents participated in this study. Parents of children with developmental disorders showed higher levels of parenting stress, depressive symptoms, and anxiety symptoms than did parents of children with typical development. Parenting stress and health worries were positively related to mental health symptoms. The association between having a child with developmental disorders and mental health symptoms was mediated by parenting stress. This study provides a timely investigation into the stress and mental health of parents during the COVID-19 pandemic. Implications on web-based parenting skills interventions, online psychological support services, and family-friendly policy initiatives are discussed.