Objective: Maternal support is an important factor in predicting outcomes following disclosure of child sexual abuse; however, definition of the construct has been unclear and existing measures of maternal support are utilized inconsistently and have limited psychometric data. The purpose of this study was to develop a reliable and valid mother-report measure for assessing maternal support following the disclosure of child sexual abuse. Methods: Data from 2 very similar samples of mother-child pairs seeking forensic evaluation following the discovery of child sexual abuse were combined, resulting in a final sample of 246. Results: Exploratory factor analysis resulted in two reliable 7-item factors labeled "Emotional Support" and "Blame/Doubt," each of which had acceptable internal consistency. Analyses with a child-report measure of general maternal support the construct validity of the MSSQ. Concurrent validity analyses revealed unique relations with maternal ratings of child behavior problems and case characteristic data. Conclusions: The study resulted in the development of a brief, easily scored self-report measure of maternal support with reasonable preliminary psychometric properties that could easily be utilized in other studies of sexually abused children. Practice implications: Adoption of this promising measure in future research will reduce the lack of cross-study measurement comparability that has characterized the maternal support literature to date, increase the feasibility of expanding upon current literature on maternal support, and may produce important information leading to clinical and theoretical innovation. (Contains 3 tables.)