Adolescent obesity has increased exponentially over the past three decades in the United States. In response, behavioral interventions have been developed and implemented to address this epidemic; however, treatment adherence is often suboptimal. Motivational interviewing (MI) is a directive, person centered approach to reducing patient ambivalence about change, which has been shown to increase engagement in obesity interventions. The current study investigated the underlying process of MI by exploring two different, but related pathways that explain how change happens (e.g., the technical and relational hypotheses) in the context of a multidisciplinary obesity intervention with African American adolescent girls (N = 30). Results demonstrated that MI-consistent skills were associated with client “change talk,” or language consistent with their desire, ability, reasons, need, taking steps or commitment to change. Specifically, clinician reflection of client change language and support of client autonomy were especially important for increasing change language. Furthermore, client language related to change was associated with three-month treatment adherence, and increased fruit and vegetable intake. However, the clinician’s ability to embody the MI “spirit” was not related to either client language or three-month treatment adherence. Findings suggest that the technical aspect of MI helps explain this approach's effects on treatment adherence among African American girls with obesity.