This study retrospectively investigated psychological factors contributing to chronic post-surgical pain (CPSP) in pediatric patients after limb-sparing or amputation surgery for extremity osteosarcoma. Psychological factors were identified and analyzed by the Wilcoxon rank-sum and median two-sample tests. Univariate and multivariate Cox regressions were performed using gender, age, psychological factors, and psychological interventions related to CPSP duration as covariates. Duration of pain treatment was significantly longer in patients resistant to psychological interventions (p = 0.01) than those receptive to interventions. Shorter duration of pain treatment was associated with older age (p = 0.03) and receptiveness to psychological interventions (HR = 4.19, 95% CI [1.22, 14.35]). Older age and receptiveness to psychological interventions as part of pain management care are associated with needing a shorter duration of pain treatment. Our results highlight the importance of prospective investigations evaluating motivation to engage in psychotherapy and psychological interventions and identify risk factors for CPSP in pediatric oncology.