Ultraviolet spectroscopy was one of the simple, rapid, cost-effective, and precise instrumental methods. The objective was the development of the U.V spectroscopy method for the validation of p-coumaric acid according to the International Council for Harmonization [Q2 (R1)] guidelines reported in this work. Antioxidant activity was performed by the DPPH (2,2-diphenyl-1-picrylhydrazyl ). The U.V method still not developed for the above drug was the research gap so validation has been studied using ethanol and phosphate buffer 6.8pH. Method A entailed the preparation of the sample and standard solutions in ethanol, whereas method B entailed the preparation of the solution in a mixture of phosphate buffer pH 6.8. Two methods were employed to select unique wavelengths for drug analysis. Method A selected 229 nm, whereas method B selected 284 nm. The drug's linearity of method A and method B was found in the concentration range of 2–10 μg/mL (R2=0.98) and 5–25 μg/mL (R2= 0.99), subsequently the accuracy of both methods by computing recovery percentages at 80, 100, and 120 percent. It was found that the recovery percentage using both approaches was between 80 and 90 percent. The lower percentage relative standard deviation (RSD) readings showed, how accurate were both approaches. The precision of the procedure was intended to be repeatable both within and between days. The fact that the % RSD value is less than 2 suggests that both approaches are accurate. With the use of ± wavelength, the robustness of both techniques was investigated. The active ingredient p-coumaric acid was included in the aqueous gel of HPMC K100M (Hydroxy methyl cellulose) and Carbopol 971p polymer and performed antioxidant activity using DDPH free radical scavenger test (IC50). The result was found to be 0.833 mg/mL. Conclusion: p-coumaric acid in pharmacologic dosage form was successfully analyzed by the U.V method and proven for significantly good anticipated antioxidant activity.