Abstract RATIONALE: Pediatric brain tumor (PBT) survivors are at risk for speech (e.g., articulation, prosody, fluency) and language (e.g., vocabulary, grammar, narratives, pragmatics) difficulties, though group outcomes vary with study design and individual risk factors (Hodges et al 2020). This study characterizes language functioning for clinically referred PBT survivors diagnosed in early childhood, a time of rapid language development and vulnerability. METHODS: Participants were 98 PBT patients (56 supratentorial) diagnosed by age 6 (M = 43.8 months, SD 24.4) who received tumor-directed intervention (surgery, chemotherapy, and/or radiation). Age at neuropsychological evaluation (2019 – 2022) was 2-19 years (M = 9.1, SD 4.1). Patients were 56% male, 73.5% White, and fluent English speakers. Verbal IQ, naming, working memory, fluency, comprehension, syntactic and phonological processing, and parent-reported functional communication outcomes were assessed. Rates of weak performance (1 SD<Mean) were compared to the expected base rate of 16%. RESULTS: Group means significantly diverged from age-expected performance in all domains except fluency. IQ correlated with most language measures, age at diagnosis (r .280, p .010), and time from diagnosis (r -.276, p .012). Weakness was identified on at least 1 verbal subtests for 71.4% of the full sample and most (57%) patients with IQ>84. Patients with NF1 (n=15) or treatment-related hearing concerns had lower reported functional communication. Naming difficulty was associated with supratentorial tumors; there were no other significant differences by tumor type or location. While functional communication correlated with several measures, weaknesses on performance-based and parent-report measures only corresponded for 44.6% of the sample. CONCLUSIONS: Language weaknesses are prevalent following early childhood PBT diagnosis. IQ and functional communication measures are useful indicators of risk, but more detailed and higher-level language measures are needed, particularly for cognitively intact patients. Additional implications and research needs will be discussed.