Psychological mindedness (PM) has long been considered to be an important mediator of therapy outcome. However, to date, definitions of PM have been typified by linguistic imprecision and lack of conceptual clarity. Further, most definitions and measures of PM have approached the task from a psychodynamic perspective, thus limiting the use of this construct by clinicians and researchers from other theoretical perspectives. In this paper, previous definitions and self-report measures are reviewed and a new definition proposed. It is argued that PM is best conceptualised as a form of metacognition: a predisposition to engage in metacognitive acts of inquiry into how and why people behave, think, and feel in the way that they do. A new model, based on this definition, suggests that PM may be assessed by measuring individuals' metacognitive processes of self-reflection and insight, circumventing many of the problems associated with previous self-report measures of PM. Research into individual differences in propensity for PM, self-reflection, and insight may well provide the clinician with additional tools with which to facilitate purposeful, directed change in both clinical and nonclinical populations.