Despite ongoing theoretical interest in the accuracy of self-knowledge and its implications for mental health, few researchers have yet to tackle this topic directly. This may be due, in part, to several factors that make assessing individual differences in accurate self-knowledge especially difficult. In this article, we present a method for the assessment of accurate self-knowledge that relies on information gathered from the self, knowledgeable others, and observations of behavior in the laboratory, and we provide psychometric support for this newly developed assessment procedure. Specifically, we present evidence for internal consistency reliability, convergent and discriminant validity, and criterion-related validity. Other researchers interested in studying the accuracy of self-knowledge might wish to adopt this procedure in their own research endeavors.