Isoniazid (INH) is a key antitubercular agent, which exhibits poor chemical stability in the solid state associated with the hydrazide group. Cocrystallization with Gentisic Acid having antioxidant activity, may produce solid forms with improved pharmaceutical properties. The complementary nature of the functional groups of isoniazid and the chosen coformer resulted in success for cocrystal formation. Cocrystal (INH-Gentisic acid) was characterized by solid-state NMR, DSC, PXRD and single crystal-XRD. The synthesized cocrystals were tested for the inhibition of synthetic-free radicals, DPPH. INH-Gentisic acid demonstrated high free radical scavenging activity against DPPH (78.36% for 125µg/ml concentration) which were better than that of ascorbic acid (37.16%) used as standard. Moreover solubility, stability and flowability properties of the synthesized cocrystals are optimized.