Introduction: Caring for a child with diabetes is a demanding and potentially stressful task for parents. Although secure attachment can be considered a resilience factor that helps an individual to cope with stressful life events, the idea that secure parents are better able to cope with a child’s chronic health condition, such as diabetes, has rarely been investigated. Therefore, the aim of this study was to investigate whether attachment-related anxiety and avoidance are associated with parenting stress in parents of children and adolescents with diabetes and whether this association is mediated by parents’ perception of the impact of diabetes on the family and moderated by children’s age and duration of diabetes. Method: A sample of 105 parents (92.4% mothers) completed self-report measures of attachment, parenting stress, and perceived impact. Results: Higher levels of attachment avoidance (but not anxiety) were associated with higher levels of parenting stress through an increased negative perception of the impact of diabetes. Discussion: This study suggests that parents with higher levels of avoidance are at higher risk of experiencing greater parenting stress and perceiving their child’s condition as more burdensome.