This study describes the relationship between parenting stress and behavior in children with Joubert syndrome, a rare genetic neurodevelopmental disorder. Parents (N = 43) reported severely impaired child adaptive behaviors. Most children did not show maladaptive behaviors, but a subset of approximately 20% displayed significant problems in areas such as inattention, overactivity, social withdrawal, and atypical behaviors. Mothers (59%) and fathers (40%) reported elevated levels of parenting stress. A hierarchical regression, including demographics, adaptive behavior, and maladaptive behavior, predicted 67% of the variance in mothers' stress and 40% of the variance in fathers' stress. Maladaptive behaviors uniquely contributed to maternal and paternal stress. The child's adaptive behavior level contributed significantly to parenting stress for mothers but not for fathers. Findings provide a better understanding of the impact of child behavior on parents caring for a child with Joubert syndrome.