Patient beliefs about health and disability are shaped by many social factors and are a key determinant in their ultimate outcome. We hypothesized that pediatric and parent-reported outcome measures regarding a child's congenital upper limb difference will be affected by geographic location, parent education, sex, ethnicity, race, age, and presence of additional medical comorbidities. Patients enrolled in the multicenter Congenital Upper Limb Difference registry were included. Age, sex, race, ethnicity, medical comorbidities, highest level of parental education, area deprivation index, and geographic region were recorded. Patient-Reported Outcomes Measurement Information System (PROMIS) in the pediatric and parent-reported domains of upper extremity, anxiety, pain interference, peer relationships, and depressive symptoms were collected. The only difference between geographic regions in the United States in pediatric and parent-reported PROMIS was that parents in the Midwest reported higher upper extremity function scores in children with upper limb differences than the West. Black patients demonstrated higher scores in parent and child-reported domains of depression, pain, and anxiety, and lower scores in upper extremity function than White and Asian peers. Additionally, children with medical comorbidities also demonstrated worse outcomes in multiple PROMIS domains. There was no difference in scores based on sex, parent education, and ethnicity. In children with congenital upper limb differences, race and additional medical comorbidities have an impact on patient- and parent-reported PROMIS outcome measures in multiple domains, with Black children and those with additional medical comorbidities scoring lower than their peers. As we strive to develop a health care system that provides equitable care to all patients, providers who care for children with upper limb differences should be aware that race and additional medical comorbidities can negatively affect patient- and parent-reported PROMIS outcome measures.