The purpose of this project was to examine the effect of the implementation of the Mystery Motivator intervention as an interdependent group contingency to decrease disruptive behavior in an urban eighth-grade general education science classroom. The study was conducted using an A-B changing criterion design. The effectiveness of the intervention was assessed for a 9-week period during which the frequency of the identified disruptive behavior decreased significantly. The teacher intervention acceptability data suggest that the teacher found the intervention to be acceptable. Data suggest that the Mystery Motivator intervention was effective for reducing targeted disruptive behaviors in an urban eighth-grade classroom. Limitations and implications for future research ideas are discussed.