Children with autism spectrum disorder (ASD) are frequently hospitalized within general psychiatric settings, which are not usually designed to meet their needs. An initial evaluation of a care pathway developed for youth with ASD receiving services in a general psychiatric inpatient unit (ASD-CP) showed promise in improving outcomes while using few resources (Kuriakose et al. in J Autism Dev Disord 48:4082–4089, 2018). As sustainability of inpatient psychiatric initiatives is imperative but rarely investigated, this study examined the stability of ASD-CP outcomes during an 18-month follow-up period (n = 15) compared to the 18-month initial evaluation (n = 20) and 18-month pre-implementation (n = 17) periods. Decreased use of crisis interventions, including holds/restraints and intramuscular medication use, was sustained in the 18 months after the initial implementation period. Implications and limitations are discussed.