A series of [Alkyl or un/substituted phenyl]-2-(3-oxo-3,4-dihydro-2H-benzo[b][1,4]thiazin-2-yl)acetamide were designed and synthesized. In vitro antifungal activity assay indicates that the 1,4-Benzothiazine has good antifungal activity against most of the tested pathogenic fungi i. e. Candida albicans, Trichophyton rubrum, Epidermophyton floccosum and Malassazia furfur. Some few compounds such as BTA-43 and BTA-56 have significant antifungal activity and broader spectrum, which are promising leads for the development of novel antifungal agents. The structures of the synthesized compounds were established on the basis of IR, NMR, 13CNMR and Mass spectra data.