Objectives: The objective of the present study is to synthesize 3-substituted phenyl-6-phenyl-7H-[1, 2, 4] triazolo [3, 4-b][1,3,4] thiadiazine. The structures of all the synthesized compounds were characterized by IR, 1H NMR and mass spectral studies.Methods: The titled compounds were synthesized by the reaction of substituted benzoic acid with thiocarbohydrazide followed by refluxing with 2-bromoacetophenone in ethanol. These compounds were evaluated for in-vitro antioxidant activity by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method.Results: Compounds 2e and 2i exhibited good antioxidant activity as compared with standard, ascorbic acid.Conclusion: In summary, 3-substituted phenyl-6-phenyl-7H-[1, 2, 4] triazolo [3, 4-b] [1, 3, 4] thiadiazine derivatives have been synthesized and characterized. In-vitro antioxidant activity of the compounds was screened by DPPH free radical scavenging method. Among the synthesized compounds, the compounds 2e and 2i have been shown the most prominent antioxidant activity using ascorbic acid as standard. The future perspective of in-vivo antioxidant evaluation of these compounds can be the potential lead.Â