Adolescents with chronic musculoskeletal pain (CMP) frequently experience pain-related stigma. The current study compared pain-related stigma across three groups of adolescents with CMP; juvenile idiopathic arthritis (JIA), chronic localized pain (CLP), and juvenile fibromyalgia (JFM). Findings supported greater pain-related stigma in adolescents with CMP with greater diagnostic uncertainty (CLP and JFM compared to JIA). These study findings highlight pain-related stigma differences for adolescents with varying CMP conditions and support a potential role for diagnostic uncertainty in explaining these differences. Youth with JFM also showed increased self-blame and expected future negative social interactions, leading to hiding their symptoms from others. Future research should continue to investigate factors contributing to differences in pain-related stigma experiences in adolescents with CMP, and ways to improve diagnostic classification to reduce medical uncertainty for adolescents with JFM.