Sensory reactivity, including hyperreactivity, hyporeactivity, and sensation seeking, is a new criterion for autism spectrum disorder (ASD) in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM‐5). However, there is no consensus on how to reliably measure sensory reactivity, particularly in minimally verbal individuals. The current study is an initial validation of the Sensory Assessment for Neurodevelopmental Disorders (SAND), a novel clinician‐administered observation and corresponding caregiver interview that captures sensory symptoms based on DSM‐5 criteria for ASD. DSM‐5 criteria of sensory hyperreactivity, hyporeactivity, and seeking behaviors are measured across visual, auditory, and tactile domains. Children with ASD showed significantly more sensory reactivity symptoms compared to typically developing (TD) children across sensory domains (visual, tactile, and auditory) and within each sensory subtype (hyperreactivity, hyporeactivity, and seeking). Psychometric properties including internal consistency, inter‐rater reliability, test‐retest reliability, and convergent validity were all strong. The SAND provides a novel method to characterize sensory reactivity symptoms based on DSM‐5 criteria for ASD. This is the first known sensory assessment that combines a clinician‐administered observation and caregiver interview to optimally capture sensory phenotypes characteristic of individuals with neurodevelopmental disorders. The SAND offers a beneficial new tool for both research and clinical purposes and has the potential to meaningfully enhance gold‐standard assessment of ASD. Autism Res 2017. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.