Abstract Objectives Individuals with bipolar disorder (BP) are often misdiagnosed with major depressive disorder (MDD). In this study, we developed a Chinese version of 15-point hypomania scale (HCL-15) in order to determine its sensitivity and specificity in the diagnosis of BP and BP-II in particular. Methods A total of 623 individuals suffering a major depressive episode (MDE) were systematically interviewed with both Structured Clinical Interview for DSM-IV-TR Axis I Disorders, Patient Edition, and HCL-15. A cutoff score of 8 or more in HCL-15 was suggested for BP. Results Of the 623 depressed patients, 115 (18.5%) actually required a diagnosis of BP-I, and another 159 (25.5%) could be more appropriately diagnosed with BP-II, according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria. The sensitivity of 15-HCL in detection of BP-II was 0.78 and 0.46 for BP-I; the specificity was 0.9 and 0.69, respectively. The specificity of HCL-15 for BP versus MDD was as high as 0.93. Approximately 60%–80% of all questions in the HCL-15 questionnaire revealed positive responses from patients, while items 11 and 12, measuring the consumption of alcohol, coffee and cigarettes, demonstrated a low positive response rate. Conclusions The HCL-15 assessment scale was fairly sensitive and highly specific for a BP-II diagnosis but not for a BP-I diagnosis. Some items in the HCL-15 symptom list need to be further modified to better fit Chinese culture and customs. The HCL-15 scale could be a useful tool in clinical practice for screening individuals with BP-II in order to avoid a misdiagnosis of MDD.