The importance of accurate identification and high-quality intervention for individuals with autism spectrum disorder (ASD) is indisputable. Clinicians from multiple professions need adequate knowledge of ASD to make appropriate referrals to specialists, conduct thorough evaluations, and provide effective interventions. ASD knowledge development for many professionals may start at the pre-service training level. An interdisciplinary sample consisting of trainees from Leadership Education in Neurodevelopmental and Related Disabilities (LEND) programs and University Centers for Excellence in Developmental Disabilities (UCEDDs) across the country (N = 155) was evaluated on their objectively measured ASD knowledge using the ASKSP-R. Self-reported knowledge of ASD and self-reported confidence in providing services to individuals who have ASD was evaluated using a 0–100 scale. Results from an ANOVA demonstrated a significant difference in objectively measured knowledge across disciplines, F(7, 146) = 4.68, p < .001. Specifically, trainees in psychology had significantly higher levels of objectively measured ASD knowledge than trainees in physical/occupational therapy, social work, and non-clinical disciplines. Pre-service and professional development experiences predicted trainees’ objectively measured ASD knowledge, self-reported ASD knowledge, and self-reported confidence. Implications and recommendations regarding interdisciplinary training to improve outcomes for individuals with ASD are discussed.