This article adds to current research by examining treatment fidelity of an evidence-based parenting program (namely Triple P) as part of a large clinical trial which included a range of procedures for promoting fidelity including both expert and peer supervision. Procedures for monitoring and promoting fidelity are described, and two major aspects of fidelity, namely content adherence and process fidelity, were evaluated. All treatment sessions for 166 families participating in the Standard Triple P-Positive Parenting Program were video-recorded and then sampled for evaluation without advanced knowledge by delivery practitioners. Independent coders at an external site assessed content adherence and rated delivery process. Fidelity promotion included high-quality training of practitioners on a standardized protocol, ongoing clinical supervision by peers and supervisors, and fidelity feedback sessions. Average content fidelity was consistently high (i.e., over 80%). Process fidelity scores were similarly high across sessions. A brief survey indicated practitioners found that the fidelity and implementation model was useful and contributed to increasing self-efficacy over the course of the initiative.