This systematic review examined the extent to which measures of religiosity/spirituality (R/S): (1) are associated with pain, function, pain-related beliefs (beliefs), coping responses, and catastrophizing in people with chronic pain; and (2) moderate the association between beliefs, coping and catastrophizing, and pain and function. Experimental and observational studies examining at least one of these research questions in adults with chronic pain were eligible. Two reviewers independently performed eligibility screening, data extraction, and quality assessment. Twenty studies were included. Most studies focused on the association between R/S and pain or function. When significant associations emerged, those between R/S and psychological function were weak to strong and positive; those between religious/ spiritual well-being and pain and physical dysfunction were negative, but weak. Few studies examined the associations between R/S and beliefs/coping/catastrophizing; none examined the moderation role of R/S. The findings suggest that R/S is associated with pain and psychological function in people with chronic pain, and that viewing oneself as being "spiritual," regardless of religion, may contribute to positive psychological adjustment. More research is needed to determine the reliability of this finding. PROSPERO registry CRD42018088803.