This paper focuses on studying the facial expressions of both client and therapist in the context of Motivational Interviewing (MI). The annotation system Motivational Interview Skill Code MISC defines three types of talk, namely sustain, change, and neutral for the client and information, question or reflection for the therapist. Most studies on MI look at the verbal modality. Our research aims to understand the variation and dynamics of facial expressions of both interlocutors over a counseling session. We apply a sequence mining algorithm to identify categories of facial expressions for each type. Using co-occurrence analysis, we derive the correlation between the facial expressions and the different types of talk, as well as the interplay between interlocutors’ expressions.