Objective This study aimed to develop and validate the Korean version of the Somatic Symptom Disorder-B Criteria Scale (SSD-12) in outpatients at a psychiatric clinic and assess its diagnostic accuracy.Methods A total of 207 patients completed SSD-12. For the diagnostic accuracy of SSD-12, the somatic symptom disorder (SSD) section of the structured clinical interview for DSM-5 disorders-research version (SCID-5-RV) was used. The SSD-12 construct and concurrent validity were assessed by examining the correlations with Generalized Anxiety Disorder-7 (GAD-7), Patient Health Questionnaire-9 (PHQ-9), PHQ-15, 5-level EQ-5D version (EQ-5D-5L), and World Health Organization Quality of Life Brief Version (WHOQOL-BREF).Results The SSD-12 had excellent internal consistency (Cronbach α=0.90). Confirmatory factor analysis revealed good fit indices for a general factor model (comparative fit index [CFI]=0.92, Tucker-Lewis index [TLI]=0.88, root mean square error of approximation [RMSEA]=0.10; 95% confidence interval [CI], 0.08–0.11) and a three-factor model (CFI=0.94, TLI=0.91, RMSEA=0.08; 95% CI, 0.07–0.10). The total SSD-12 score was significantly correlated with anxiety (GAD-7: r=0.53, p<0.001), depression (PHQ-9: r=0.52, p<0.001), physical symptom burden (PHQ-15: r=0.36, p<0.001), and quality of life (EQ-5D-5L: r=-0.40, p<0.001; WHOQOL-BREF: r=-0.51, p<0.001). SSD-12 demonstrated good accuracy (area under the curve=0.75, standard error=0.04; 95% CI, 0.68–0.82) with an optimal cut-off of 29.Conclusion The Korean SSD-12 demonstrates reliability and validity for diagnosing SSD in clinical setting.