A central concern raised by many patients attending a pediatric chronic pain interdisciplinary clinic is physical functioning decline, fatigue, and diminished endurance. However, most studies examining treatment effects of pain programs on physical outcomes have relied on self- and/or parent-reported measures without confirming the results using objective indices, and predictors of objective indices of physical function in this population have rarely been examined. The purpose of the present study was to evaluate changes in objective physical functioning and to investigate psychosocial predictors of physical functioning over time in a sample of pediatric patients who completed an intensive outpatient pain program (IOP). Participants (N=55; Mage=14.92 years; 12.7% male, 87.3% female; 83.6% White, 5.6% African-American/Black; 9.1% Latinx) completed baseline measures assessing pain levels (Brief Pain Inventory), anxiety/depressive symptoms (Hospital Anxiety and Depression Scale), pain catastrophizing (Coping Strategies Questionnaire), and kinesiophobia (Tampa Scale for Kinesiophobia). Participants completed the FitKids Treadmill Test (FitKids) assessing physical endurance and the high-level mobility assessment tool (HiMAT) assessing physical ability pre- and post-IOP completion. Paired samples t-tests indicated significant improvement in Total Time to Exhaustion (TTE) on FitKids (p .138). Participation in an IOP led to significant improvement in physical endurance and ability. Depressive symptoms were negatively associated with endurance at baseline but not after program completion. Depressive symptoms may influence pre-treatment objective physical endurance and should be assessed in pediatric chronic pain patients beginning rehabilitation.