A new, simple, rapid, selective, precise and accurate isocratic reverse phase high performance liquid chromatography assay has been developed for simultaneous estimation of various tablet formulations. The separation was achieved by using C-18 column (Phenomenax, 250 x 4.6mm i.d.) coupled with a guard column of same material, in mobile phase Acetonitrile: Water (25:75). The pH of mobile phase was adjusted to 6.0 ± 0.1 with 50% ortho phosphoric acid. The flow rate was 1.0 mL.min-1 and the separated drugs were detected using UV detector at the wavelength of 300 nm. The retention time of various formulations was noted to be 2.08 and 5.05 min, respectively for Levothyroxine and Liothyronine, indicative of rather shorter analysis time. The method was validated as per ICH guidelines. The proposed method was found to be accurate, reproducible, and consistent. It was successfully applied for the analysis of these drugs in marketed formulations and could be effectively used for the routine analysis of formulations containing any one of the above drugs, or a combination, without any alteration in the chromatographic conditions.