Motivational interviewing has become widely adopted as a counseling style for promoting behavior change; however, as yet it lacks a coherent theoretical framework for understanding its processes and efficacy. This article proposes that self-determination theory (SDT) can offer such a framework. The principles of motivational interviewing and SDT are outlined and the parallels between them are drawn out. We show how both motivational interviewing and SDT are based on the assumption that humans have an innate tendency for personal growth toward psychological integration, and that motivational interviewing provides the social-environmental facilitating factors suggested by SDT to promote this tendency. We propose that adopting an SDT perspective could help in furthering our understanding of the psychological processes involved in motivational interviewing.