Treatment adherence and nonadherence is the current paradigm for understanding why people with serious mental illnesses have low rates of participation in many evidence-based practices. The authors propose the concept of self-determination as an evolution in this explanatory paradigm. A review of the research literature led them to the conclusion that notions of adherence are significantly limited, promoting a value-based perspective suggesting people who do not opt for prescribed treatments are somehow flawed or otherwise symptomatic. Consistent with a trend in public health and health psychology, ideas of decisions and behavior related to health and wellness are promoted. Self-determination frames these decisions as choices and is described herein via the evolution of ideas from resistance and compliance to collaboration and engagement. Developments in recovery and hope-based mental health systems have shepherded interest in self-determination. Two ways to promote self-determination are proffered: aiding the rational actor through approaches such as shared decision making and addressing environmental forces that are barriers to choice. Although significant progress has been made toward self-determination, important hurdles remain.