Although spirituality often has been associated with better outcomes following bereavement, it can be significantly challenged by loss as well. Studies have shown that some bereaved individuals suffer profoundly not only in relation to the death of their loved one but also in their relationship with God and their faith community, a condition known as complicated spiritual grief (CSG). However, to date, in the absence of a simple, multidimensional, and well-validated measure of spiritual crisis following loss, investigators have measured CSG with nongrief-specific instruments. In this study, the authors tested the reliability and validity of a newly developed measure of CSG, called the Inventory of Complicated Spiritual Grief (ICSG). With 2 diverse samples of bereaved adult Christians (total n = 304), the authors found that the ICSG had strong internal consistency, and high test-retest reliability for both subscales in a subsample of participants. Analyses of both samples supported a 2-factor model, with one factor measuring Insecurity with God and the other assessing Disruption in Religious Practice. Analyses further supported the convergent and incremental validity of the 18-item ICSG relative to other theoretically similar instruments and measures of poor bereavement outcome, suggesting its usefulness in clinical research and practice.