Motivational Interviewing is an evidence-based brief intervention for helping people change problematic health behaviors. The development of motivational interviewing was influenced, in part, by the social psychology literature, especially the concept of psychological reactance. This paper argues for expanding the influence of social psychological processes upon the practice of motivational interviewing by reviewing three relevant processes: defensive bias, message framing, and cognitive-affective ambivalence. Relevant research findings are reviewed and specific recommendations are offered for future research and enhancing the practice of motivational interviewing.