BACKGROUND/OBJECTIVES: Survivors of pediatric brain tumors (BT) are at increased risk for difficulties with social competence, including poor social information processing (SIP) and peer relationships. Due to improved survival rates among BT, there is a need to better understand these challenges and if they are specific to BT versus other survivors of childhood cancer. METHODS: 51 BT and 34 survivors of pediatric solid tumors (ST) completed evaluations of SIP and peer relationship quality within 6 months of completing treatment and at one year follow-up. Caregivers also completed a measure of social skills. Linear mixed models evaluated (1) differences between BT and ST on SIP and social skills and (2) how indices of SIP were associated with peer relationships over time for ST and BT. RESULTS: BT did not differ from ST on indices of SIP or social skills over time. There was a three-way interaction between measures of SIP, group, and time to predict peer relationships. ST showed a positive association between baseline social skills and theory of mind and peer relationships over time, whereas BT showed an inverse association between baseline social skills and theory of mind and peer relationships over time. CONCLUSION: Baseline SIP and social skills affected the trajectory of BT peer relationships. BT social functioning should be monitored regularly after the completion of treatment to determine if and when intervention services would be beneficial.