The purpose of this pilot study was to examine preliminary feasibility, acceptability, and effectiveness of a toolkit (Parent And Caregiver Active Participation Toolkit) to increase parent participation in community-based child mental health services. Study participants included 29 therapists (93% female; M age = 34.1 years; 38% Latino) and 20 parent/child dyads (children 80% female; M age = 8.6 years; parents 40% Latino) in 6 diverse community mental health clinics. Therapists were randomly assigned to standard care or the toolkit with standard care. Therapist and parent survey data and observational coding of treatment sessions were utilized. Mean comparisons and repeated measures analyses were used to test differences between study conditions over 4 months. Results supported preliminary feasibility and acceptability of the toolkit, with therapists assigned to the toolkit participating in ongoing training, adhering to toolkit use, and perceiving the toolkit as feasible and acceptable within their setting. Results preliminarily demonstrated improvement in therapists' job attitudes, as well as actual use of parent engagement strategies. Results also preliminarily demonstrated increases in parent participation in child therapy sessions and more regular attendance, as well as some indication of support for perceived treatment effectiveness. Overall, results suggest the feasibility, acceptability, and potential effectiveness of the toolkit to enhance therapist job attitudes; practices that support parent engagement, parent engagement itself, and consumer perspectives on treatment outcomes; and the potential promise of future research in the area of parent participation interventions in child mental health services.