Roots of Withania somnifera are widely used in Indian herbal formulations. Withaferine A and withanolide A are two pharmacologically important withanolides present in the roots of the plant. HPLC method using DAD and ELSD detector was developed for simultaneous determination of withaferine A and withanolide A from the roots and herbal formulation of the plant. Coarse powder of root was extracted with methanol by shaking for 30 minutes and sonication for 45 minutes. Herbal formulation was first extracted with chloroform and then with ethyl acetate, extracts were combined, evaporated and reconstituted with methanol. Retention time of both the compounds was vary with detector to detector and it was found for withaferine A (3.74, 3.84 min) and withanolide A (4.51, 4.60 min) with DAD and ELSD detector, respectively. Amount of withanolides in each sample were calculated from the regression equations of standard calibration graphs. The results showed that the HPLC method is suitable for the determination of withaferine A and withanolide A from the roots and herbal formulation of W. somnifera.