The purpose of this study was to evaluate emotion dysregulation and temperament-character traits in adolescents with functional neurological symptom disorder (FNSD). Forty adolescents with FNSD and 40 healthy adolescents were evaluated by a semiconstructed diagnosis interview, Temperament and Character Inventory (TCI), Difficulties in Emotion Regulation Scale (DERS), Regulation of Emotions Questionnaire (REQ), and Children’s Somatization Inventory-24 (CSI-24). The external and internal dysfunctional emotion regulation scores of REQ, all subscales of DERS, except the awareness subscale, and CSI-24 scores were significantly higher in FNSD patients compared with healthy controls. There were significant differences between the groups in terms of harm avoidance and reward dependence subscale scores of TCI. Multiple logistic regression analysis showed that the external dysfunctional emotion regulation strategy, somatization, and reward dependence are significant predictors of FNSD. Our results provide evidence that adolescents with FNSD experience emotional dysregulation and that the differential value of some temperament-character traits in the diagnosis of FNSD.