A simple UV–visible spectrophotometric method was developed and validated for the quantitative estimation of sulfamethoxazole in tablet dosage forms in accordance with ICH guidelines (ICH, 2005). The method employs filtered water as solvent and measurement of absorbance at 525 nm, with calibration curves showing good linearity over the concentration range of 5–30 μg mL−1μg mL−1. Absorptivity values were calculated at the selected wavelength. Accuracy, evaluated through recovery studies, showed percent recovery between 98.90 and 99.96% with %RSD values below 2%, confirming the reliability of the method. Precision studies (intra- and inter-day) yielded a %RSD of 0.678, while ruggedness assessment using six replicate absorbance measurements produced a %RSD of 0.253, indicating good robustness. All validation parameters met ICH acceptance criteria, demonstrating that the proposed method is simple, rapid, accurate, precise, and suitable for routine quality control analysis of sulfamethoxazole in pharmaceutical tablet formulations.