This study illustrates development and validation of a simple high performance liquid chromatographic method for the simultaneous determination of metformin hydrochloride and angiotensin-converting enzyme inhibitors (captopril, lisinopril, and enalapril) in bulk dosage form and their application in pharmacokinetic studies. The quality resolute chromatogram was obtained by using a Purospher® Star RP-18 endcapped (250 × 4.6 mm id) column as stationary phase while acetonitrile-water 50:50 (v/v) as mobile phase, adjusted to pH 3.0 with phosphoric acid. Effluent was monitored at a flow rate of 1 mL min−1 at room temperature (25 °C), detector was set at 218 nm. The method was validated according to ICH guidelines. The linearity was studied over the concentration range of 10–10,000 ng mL−1 for metformin and 30–10,000 ng mL−1 for captopril, lisinopril, and enalapril, demonstrating good linearity with minimum r = 0.9964, respectively. The developed method was successfully applied to pharmacokinetic studies of metformin, lisinopril, captopril and enalapril.