This article presents results from an investigation using functional assessment strategies in a general education classroom for an early adolescent diagnosed with ADHD/ODD. In the first phase of the assessment, data were collected from teacher interviews, student interviews, and direct observations to generate hypotheses regarding the association between classroom environmental conditions and the occurrence of disruptive behavior. The hypotheses were then evaluated in the context of regularly occurring classroom activities. Based on the data obtained through the functional assessment procedure, a classroom intervention was designed, implemented, and evaluated. Results indicated the intervention was successful in decreasing the participant's disruptive behavior. Further, the teacher and student reported high acceptability for the assessment and intervention. Project findings are discussed in terms of bridging the gap between research and practice, conducting a functional behavioral assessment (FBA) within applied settings, and the use of FBA for behaviors that are potentially under the control of multiple maintaining functions.