Parent participation in community-based child mental health services is an important yet understudied process associated with treatment effectiveness. This paper describes the development and psychometrics of the Parent Participation Engagement Measure in a sample of 1374 parents and 563 youth receiving publicly-funded mental health services. Analyses indicated excellent internal consistency, and model fit indices/factor loadings supported a one-factor model. Convergent and discriminant validity were supported, although some coefficients were modest in magnitude. Psychometric results were consistent for Caucasian versus Hispanic, parent versus youth, and English versus Spanish-language respondents. The clinical and research utility of this measure are discussed.