Separation of Atenolol and Chlorthalidone was successfully achieving thermal, C18, 250X4.6mm, 5µm, or equivalent in an isocratic mode utilizing 0.1M KH2PO4: Methanol (65:35) at a flow rate of 1.0ml/min and elute was monitored at 256nm, with a retention time of 3.346 and 3.931 minutes for Atenolol and Chlorthalidone respectively. The method was validated and their response was found to be linear in the drug concentration range of 50µg/ml to150 µg/ml for Atenolol and 50µg/ml to150 µg/ml for Chlorthalidone. The values of the correlation coefficient were found to 0.999 for Atenolol and 0.999 for Chlorthalidone respectively. The LOD and LOQ for Atenolol were found to be 0.110 and 0.366 respectively. The LOD and LOQ for Chlorthalidone were found to be 0.0818 and 0.2728 respectively. This method was found to be a good percentage recovery for were found to be 100 and 100 respectively indicates that the proposed method is highly accurate. The specificity of the method shows good correlation between retention times of standard with the sample so, the method specifically determines the analyte in the sample without interference from excipients of tablet dosage forms. The method was extensively validated according to ICH guidelines for Linearity, Accuracy, Precision, Specificity, and Robustness.