A simple, rapid, accurate and precise spectrophotometric method is proposed for the determination of atenolol in both pure form and in its pharmaceutical formulation. The method is based on the oxidation of atenolol with chromate in acidic medium of 1N H2SO4, the residual amount of oxidizing agent is then reacted with indigo carmine dye in the presence of oxalate as a catalyst, the increase in the absorbance of the dye, which is proportional to the amount of the determinants atenolol is then measured at 610 nm. Beer's law is obeyed in the concentration range of 30-1500 µg/25 ml with a molar absorptivity of 0.73×104 l.mol-1.cm-1, Sandell's sensitivity index of 0.364 μg.cm-2, and a relative standard deviation of ± 0.263 to ± 0.376% depending on the concentration level. The limit of detection (LOD) and limit of quantification (LOQ) are 0.3259 and 1.0863 μg ml−1, respectively. The proposed method has been applied successfully to the determination of atenolol in pure and pharmaceutical preparation..