Although augmentative and alternative communication (AAC) strategies are often used by autistic youth, little is known about the use of AAC in inpatient psychiatric settings. This study evaluated how demographic and clinical factors (e.g., language level, IQ) related to AAC use in a well-characterized sample of 527 autistic youth (78.7% male, mean age 12.94) who participated in the Autism Inpatient Collection. AAC use was common, with 42.5% of caregivers reporting at least one form of AAC. White children were more likely to use AAC than non-white children at the bivariate level. In regression analyses, young children were more likely to use AAC than older children. These results suggest the importance of provider training and improved equitable access to AAC.