Objective: To determine the prevalence, course, and predictors of posttraumatic stress disorder (PTSD) in mothers and fathers of children with newly diagnosed type 1 diabetes. Method: Forty-nine mothers and 48 fathers of 52 children (response rate 65%) with newly diagnosed diabetes (age 6.5-15 years) were assessed at 6 weeks, 6 months, and 12 months after the diagnosis with the Posttraumatic Diagnostic Scale. Results: The prevalence of current PTSD in mothers was 22.4% at 6 weeks, 16.3% at 6 months, and 20.4% at 12 months. In fathers, PTSD was found in 14.6%, 10.4%, and 8.3%, respectively. Mothers endorsed more symptoms of PTSD at all assessments. Multivariate analyses controlling for demographics, metabolic control, and threat appraisals revealed that in mothers, the number of preceding life events and PTSD symptoms at 6 months predicted PTSD at 12 months. In fathers, PTSD severity at 6 months was the only significant predictor for PTSD at 12 months. Conclusions: The results suggest that the diagnosis and treatment of diabetes in their child constitute traumatic events for parents. The findings confirm the applicability of a posttraumatic stress model for investigating the psychological impact of diabetes on parents. J. Am. Acad. Child Adolesc. Psychiatry, 2005;44(7):682-689. Key Words: chronic illness, childhood illness, diabetes mellitus, posttraumatic stress disorder, parental mental health.