An LC-MS/MS Bioanalytical approach has been established to develop a sensitive and quick method for quantifying Agomelatine in human plasma. As an internal standard, Agomelatine d6 was utilized. Ethyl acetate was used to extract agomelatine and internal standard from a plasma sample by liquid-liquid extraction.The upper layer was centrifuged, evaporated, and reconstituted using methanol:5mM ammonium acetate (80:20, v/v) to serve as the mobile phase. Inertsil C18 (50 x 4.6 mm, 5 m) GL Sciences (make) column was used in the method. Multiple reaction monitoring (MS/MS) was used to identify Agomelatine and Agomelatine d6 in human plasma without significant interference from the matrix.