What is a professional psychologist to do when a client brings up the concept of sin? To some, sin may seem like a stifling religious relic that has no place in contemporary psychology. But viewing sin from within the Christian faith, and in tandem with the doctrine of grace, can help psychologists understand why sin is such an important concept for many of their Christian clients. Psychologists' misunderstanding of sin and grace may contribute to relatively low rates of referral from Christian leaders to clinical psychologists, and may sometimes hinder therapeutic progress. Two methods of data collection, involving a total of 171 respondents, were used to discern what Christian leaders wish psychologists understood regarding the doctrine of sin. Respondents emphasized the nature and consequences of sin, grace, and the importance of psychologists understanding sin and grace. Implications for professional psychologists are offered.