Perceived stigma has been shown to be related to poorer quality of life, higher levels of depression, and lower social support availability in various types of chronic illness. In the area of chronic pain specifically, there is growing evidence that patients suffering from functional somatic syndromes report relatively high levels of perceived stigma and depressive symptoms compared to patients with well-established medical diagnoses. The goal of this study was to examine the effects of diagnosis, perceived stigma, and perceived social support on depressive symptoms in a sample of chronic pain patients. A sample of 112 female fibromyalgia (FM) and osteoarthritis (OA) patients was assessed longitudinally with a 1.5-year interval between initial and follow-up assessment. The results show that FM patients reported higher levels of depression and perceived stigma, and lower levels of perceived social support compared to OA patients. Hierarchical regression analyses provided support that perceived stigma contributes significantly to the prediction of depression over and above the effects of pain and other control variables. Diagnosis was found to moderate the relationship between stigma and depression so that FM compared to OA patients had greater increases in depressive symptoms with increased levels of perceived stigma. Mediational analyses showed that perceived social support mediates the relationship between the interaction of stigma by diagnosis, and depressive symptoms. Longitudinal analyses failed to show that perceived stigma predicts future levels of depression over and above initial depression levels. The practical and theoretical implications of these results are discussed.