Objective: Herbal formulations are popular in worldwide due to safer and not causing any toxicity. Recently there have been reported herbal medicines adulterated with undeclared synthetic drugs. A simple, specific, accurate and isocratic RP-HPLC method was developed and subsequently validated for determination of adulterant. Methods: Separation was achieved with a Phenomax Luna C¬18 (250 × 4.5 mm) 5μm column with a mobile phase comprising phosphate buffer: Acetonitrile pH-4 adjusted with 0.1% ortho phosphoric acid in the volume ratio of (45:55% v/v) was developed. The detection was carried out using a photo diode array detector set at a wavelength of 254 nm. Results: The method was validated as per ICH guideline demonstrating the accuracy and precision within corresponding linearity range of 10 μg/ml to 60 μg/ml and get the correlation coefficient of paracetamol, diclofenac sodium and aceclofenacwerefound to be 0.995, 0.997, and 0.995, respectively. Conclusion: The developed method was validated with respect to linearity, accuracy, precision limit of detection and quantification and robustness. The method can be used for quality control of herbal formulation.