Cognitive-behavioural models of obsessive-compulsive disorder (OCD) propose that inflated responsibility beliefs are central to the maintenance of the disorder and are proposed to originate during early childhood via experiences of harsh and/or controlling parenting. The current study aimed to examine the associations between perceived parental rearing behaviours, inflated responsibility/threat beliefs, and OCD severity and impairment in children (aged 7-12 years) and adolescents (aged 13-17 years) with OCD (n = 136). Results indicated that for younger children, greater child perceptions of overprotection and anxious rearing were each associated with increased inflated responsibility beliefs. For older children, these positive associations remained, and furthermore, inflated responsibility beliefs mediated the association between perceived maternal anxious rearing and OCD impairment. Results highlight the role of the family in the development of inflated responsibility bias and OCD-related impairment.