Background: Previous clinical and theoretical work supports the idea that parental attachment style and complicated grief affect young persons' mental health, but empirical research investigating their impact on young person's adjustment to bereavement is lacking. Objective: This study investigated the impact of parental attachment style and complicated grief on young person's adjustment to bereavement. It was hypothesised that a) parental attachment anxiety, avoidance, and complicated grief would moderate the link between bereavement experience and psychological distress in young persons and b) parental attachment style would moderate the link between parental complicated grief and psychological distress experienced by bereaved young persons. Method: This was a questionnaire-based case control study, involving two participant groups: 133 parents of young persons who had experienced the loss of the loved one and 101 parents of young persons with no bereavement experience. Results: Bereaved young persons experienced greater externalising and internalising problems than the non-bereaved only when they were raised by an anxiously attached parent, but when parental attachment anxiety was low, bereaved children had fewer problems than the non-bereaved. When parental attachment avoidance was low, bereaved children also had fewer externalising problems than the non-bereaved. Among the bereaved, high levels of parental attachment anxiety and attachment avoidance amplified the link between parental complicated grief and child post-traumatic stress, while in the presence of low parental anxiety, complicated grief was negatively associated with an immediate distressing response and numbing-dissociative symptomatology. Conclusions: Psychological vulnerability in bereaved young persons was associated with an insecure parental attachment style.