A reliable and reproducible reversed-phase high performance liquid chromatography (RP-HPLC) was developed for the quantitative determination of Quetiapine Fumarate from marketed bulk tablets. The active ingredient of Quetiapine Fumarate separation achieved with C18 column using the methanol water mobile phase in the ratio of 30:70 (v/v). The active ingredient of the drug content quantify with UV detector at 359 nm. The retention time of Quetiapine Fumarate is 5.27 min. A good linearity relation (R2=0.999) was obtained between drug concentration and average peak areas. The limit of detection and limit of quantification of the instrument were calculated 0.02 and 0.06 μg/mL, respectively. The accuracy of the method validation was determined with the inter-day (100.28 %) and intra-day (100.48 %) recoveries of the drug. The quantification correlation range was 5-50 ppm. The new method was validated according to international conference harmonization guidelines