This study outlines a straightforward, cost-effective, and sensitive stability-indicating reverse phase high-performance liquid chromatography (RP-HPLC) method for the simultaneous quantification of cilnidipine (CNG) and olmesartan (OMS) in bulk and pharmaceutical formulations. The analysis was performed on an octa-decyl C18 column (5 μm, 25 cm x 4.6 mm, i.d) with a mobile phase consisting of 70% acetonitrile (ACN) and 30% 0.1% orthophosphoric acid (OPA) at a flow rate of 1.0 ml/min. Detection was carried out at a wavelength of 257 nm, which was found to be suitable for both cilnidipine and olmesartan. The retention times were 2.78 minutes for cilnidipine and 4.89 minutes for olmesartan. The regression equations for cilnidipine and olmesartan were y=12352x−7105 and y=6634.9x+11282, with correlation coefficients (R2) of 0.999 and 0.9989, respectively. This developed method is robust, accurate, and sensitive, making it suitable for the estimation of cilnidipine and olmesartan in combined pharmaceutical dosage forms.