A novel HPLC method was proposed for the quantitation of vortioxetine, which is a new antidepressant drug, in tablets. Separation was performed on a Zorbax Eclipse Plus C18 (3.5 mu m particles, 4.6 x 50 mm) column at 35 degrees C with 1.0 mL/min flow rate and chlorpromazine was selected as internal standard. Box-Behnken design, a design of experiment (DoE) method, was applied to explore the influences of mobile phase pH, acetonitrile content and buffer concentration on chromatographic separation of vortioxetine and chlorpromazine. The optimized conditions were acetate buffer (25 mM, pH:4):acetonitrile (63.5:36.5, v/v). Retention times of chlorpromazine and vortioxetine were 3.8 and 4.6 min, respectively, and a good chromatographic separation was obtained under optimal conditions. Validation studies of the developed method were conducted according to the International Conference on Harmonization (ICH) guideline. The method was linear in the concentration range of 0.5-50 mu g/mL. The detection and quantitation limits were 0.080 and 0.264 mu g/mL, respectively. Recovery values within 98-102% and relative standard deviation values lower than 2% indicate the precision and accuracy of the method. The method was applied to vortioxetine tablets with no interference.