An accurate, simple and precise RP-HPLC method for the simultaneous estimation sulfadiazine and trimethoprim in pharmaceutical formulations was developed and validated. Chromatographic separation of two drugs was achieved on PEAK 7000 isocratic HPLC with rheodyne manual sample injector by using the mobile phase consisting of methanol, water and aceticacid in the ratio 70:25:05 (v/v/v) at a flow rate of 1mL/min and the wavelength of detection was at 237 nm. The retention time for sulfadiazine and trimethoprim were found to be 4.24 and 7.25 min respectively. The linearity of the method was tested over a concentration range of 41-287 µg/mL for sulfadiazine and 9-63 µg/mL for trimethoprim and the correlation coefficient was 0.999 for sulfadiazine and 0.998 for trimethoprim which is almost equal to 1. The limit of quantification was 3.5 μg/mL for sulfadiazine and 1 μg/mL for trimethoprim and the limit of detection was 1 μg/mL for sulfadiazine and 0.3 μg/mL for trimethoprim. The percentage recoveries were ranged from 98.64-101.64 for sulfadiazine and 98.56-100.86 for trimethoprim.