This article presents the psychometric properties of the Expanded School Mental Health Collaboration Instrument [Community Version], a measure for assessing collaboration from the perspective of community-based mental health professionals working in schools. A three-scale instrument (Types of Collaboration, Influences on Collaboration, and Perceived Benefits of Collaboration) was developed based on findings from focus group interviews and a review of the literature. This instrument complements an existing measure of collaboration that considers the perspectives of school professionals involved in expanded school mental health (ESMH). Exploratory factor analyses were used to define a set of factors for each of the three scales. Preliminary psychometric examination suggests this is a promising instrument that should be studied further. Implications for ESMH practitioners and researchers are proposed.