A dispersive micro-solid phase extraction (D-mu-SPE) method based on polystyrene coated magnetic nanoparticles (PS@MNPs) was used to preconcentrate the active ingredients of three antidepressant drugs from aqueous solution to be determined by gas chromatography mass spectrometry. Eight prominent parameters of the D-mu-SPE method were optimized univariately to boost the recovery and extraction efficiency of the analytes. The three analytes recorded very low detection limits between 0.40 and 0.60 ng/mL, and the dynamic range was broad with high linearity. Medical wastewater was selected as test sample to evaluate the method's applicability and accuracy, and the percent recovery results obtained ranged between 90 and 98 % for two different spike concentrations. The proximity of the recovery results to 100 % and the low standard deviations validated the developed method's accuracy and precision, respectively.