Social motivation in individuals with ASD is currently derived from the observation of overt behaviors and neurological correlates, from which motivational processes are inferred. Motivation, however, is not the same as behavior, and most theoretical conceptualization of the construct assign primary importance to cognitive processes. Nevertheless, few studies have examined the cognitive processes that may influence goal-directed tasks involved in social interaction. Understanding internalized cognitive processes may distinguish underlying motivations which influence engagement in social behavior. This study aims to assess how beliefs, mindsets, and attitudes can influence one's motivation to engage in social interaction through the development of a novel interview. The Social Motivation Interview (SMI) assesses for internal cognitions as they relate to social motivation by determining levels of social desire, interest, and behaviors in children with ASD. The development of the SMI followed stringent criteria to create a unified measure that was methodologically sound and theoretically informed. SMI development followed guidelines to ensure item pool development was consistent with the proposed construct. Pilot testing suggested feasibility of administration, user satisfaction, and promising psychometric properties. Future examination of the SMI in large-scale field testing is warranted.