Introduction: Neurodevelopmental and executive functioning deficits place survivors of critical congenital heart defects (CHD) at risk for poor adaptive outcomes. Peer relationships play a critical role in development, but have received little scientific attention in CHD. Brief, general ratings of ‘social problems’ by children and parents inconsistently identify difficulties, but lack the rigor and specificity of school-based sociometric methods that identify impairment in other children with acquired brain injury. Our objective was to compare the peer interactions and social adjustment of CHD survivors to healthy control classmates (CC) using school-based methods. Hypothesis: CHD survivors would be higher in victimization, isolation, and disruptive behavior, lower in peer acceptance and mutual friendships than CC. Method: Data were collected in the classrooms of 34 children (9-12 yoa, 68% male) with critical CHD (dTGA, TOF, HLH/SVA, coarctation of aorta). One CC, matched for gender and age, was identified per class. Classmates with parental consent (N=723, 89% available) rated each other using the Extended Class Play (ECP; nominations of social and nonsocial attributes), Peer Acceptance Ratings (1-5, “like a lot” to “don’t like a lot”), and named Three Best Friends. Self-ratings were made on the PROMIS Peer Relationships scale. Teachers completed the Teacher Report Form (TRF). Independent two-tail t-tests compared the CHD and CC groups. Results: CHD survivors were higher in Victimization ( d = 0.76, p = 003) and Isolation ( d = 0.46, p = .063) but not Aggressive-disruptive behavior ( d = 0.09, p = .674) on the ECP. CHD survivors had fewer mutual friends ( d = -0.62, p = .015) but not lower Peer Acceptance ( d = 0.24, p = 325). The ECP found that CHD survivors were seen as doing worse academically ( d = -0.61, p = .014) and athletically ( d = -0.99, p = .000) than CC, but not seen as more “ill” (tired, sick, or absent) ( d = -0.30, p = .215). Differences on the PROMIS were not found. TRF for the CHD group suggested Social Problems ( M T = 55.6) and Academic deficits ( M T = 45.4) but not Internalizing ( M T = 51.4) or Externalizing ( M T = 51.2) behavior. Conclusion: Peer relations of children with critical CHD are a concern, may signal further developmental risk, and warrant more study.