Customer engagement marketing—defined as a firm’s deliberate effort to motivate, empower, and measure customer contributions to marketing functions—marks a shift in marketing research and business practice. After defining and differentiating engagement marketing, the authors present a typology of its two primary forms and offer tenets that link specific strategic elements to customer outcomes and thereby firm performance, theorizing that the effectiveness of engagement marketing arises from the establishment of psychological ownership and self-transformation. The authors provide evidence in support of the derived tenets through case illustrations, as well as a quasi-experimental field test of the central tenet of engagement marketing.