Although functional analysis is a widely researched tool for determining behavioral function, traditional formats are associated with limitations that often preclude their incorporation into practice. The interview-informed synthesized contingency analysis (IISCA) was developed to address such limitations. This study investigated the effectiveness and efficiency of the IISCA in determining the function of problem behavior for three non-vocal children with autism spectrum disorder and intellectual disabilities in a school setting. The effectiveness of the skill-based treatment process associated with the IISCA was also evaluated, as were the acceptability of these treatment procedures and the fidelity with which they were implemented. The IISCAs yielded differentiated outcomes immediately for two participants and following a secondary analysis for the third participant. Assessment results informed the design of treatments involving functional communication training and delay- and denial-tolerance training evaluated using a changing-criterion design. Implications and limitations are discussed and recommendations for future research are offered.