This study investigated the relationship among spiritual competencies, personal spiritual beliefs, and clinical supervision in spirituality with professional psychology predoctoral interns. It was hypothesized personal spiritual beliefs and supervision in spirituality would be predictors of spiritual competencies in clinical practice. Social desirability was assessed as a possible confounding variable. Participants consisted of predoctoral psychology interns from APA-accredited and APPIC internship sites in the United States. The findings of this study show both personal spiritual beliefs and graduate supervision in spirituality are predictors of spiritual competency. Supervision in spirituality was a stronger predictor than personal spiritual beliefs. Social desirability was not found to be a confounding variable. These results can be used to inform training and increase levels of spiritual competency in professional psychology predoctoral interns. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]