This study explored the association between coaching and the implementation of the Good Behavior Game (GBG) by 129 urban elementary school teachers. Analyses involving longitudinal data on coaching and teacher implementation quality indicated that coaches strategically varied their use of coaching strategies (e.g., modeling, delivery) based on teacher implementation quality and provided additional support to teachers with low implementation quality. Findings suggest that coaching was associated with improved implementation quality of the GBG. This work lays the foundation for future research examining ways to enhance coach decision-making about teacher implementation. [This paper was published in "Administration and Policy in Mental Health and Mental Health Services Research" v40 n6 p482-493 2013.]