Abstract Objective Given the high levels of pain and low rates of treatment adherence in children with juvenile idiopathic arthritis (JIA) and their families, this study sought to examine the relationship between parent pain cognitions (i.e., pain catastrophizing, fear of pain) and treatment adherence, and how barriers to treatment (e.g., forgetting treatments, children resisting injections) may be implicated in this relationship. Methods Parents of children under 18 years of age who have been diagnosed with JIA were recruited to complete an online survey. In total, 221 parents (93% mothers) of children aged 2–17 years (M = 11.10, SD = 4.25) took part, completing questions regarding their pain cognitions, perceived barriers to treatment, and their child’s arthritis treatment adherence ability. Results Hierarchical regressions demonstrated that both pain cognitions (i.e., pain catastrophizing and fear of pain) were related to a decrease in parent-reported treatment adherence, however, pain catastrophizing was no longer significant when fear of pain was added to the model. The presence of treatment barriers partially mediated the relationship between fear of pain and treatment adherence, above and beyond the alternate model proposed. Conclusion These results suggest that parent pain catastrophizing and fears of pain are related to a greater difficulty following treatment plans, possibly in part because of barriers parents experience that preclude adherence. Given these findings, the identification and management of parent pain cognitions is critical to improving treatment adherence and outcomes for children with JIA and their families.