An effective and sensitive liquid chromatographic-electrospray ionization tandem mass-spectrometric (LC-ESI-MS/MS) method was developed and validated for quantification of escitalopram oxalate (ESC-OX), antidepressant drug in spiked human urine and pharmaceutical formulations. In this work, simple liquid-liquid extraction was optimized and used for extraction of cited drug from urine samples. The chromatographic separation was attained within 6 min including re-equilibration time by using gradient elution with 0.1% formic acid in acetonitrile and 0.1% formic acid in water as mobile phase, Zorbax Eclipse RP C-18 (50 x 2.1 mm) column was used with a particle size of 1.8 mu m; the flow-rate was 0.35 mL min(-1). Ion signal m/z 262.0 and 109.0 for ESC-OX product ions were monitored at positive ESI mode. Validation of the method was carried out according to the ICH Q2 (R1) guidelines and EMEA criteria. The method was linear over 79-196,450 pg mL(-1) with a regression of 0.9999 and 0.9993 for both standard and urine samples. The LOD was 3.88 and 10.66 pg mL(-1) for standard and urine samples, respectively, while lower limit of quantification was 79 pg mL(-1).