A series of 6-substituted phenyl thiazolo-1,2,4-triazinones (8) were obtained by the initial reaction of 6-substituted arylmethyl-3-mercapto-1,2,4-triazin-5-ones (5) with substituted phenacyl bromides (6) and further followed by PPA cyclization. The structures of the newly synthesized compounds were confirmed by IR, (1)H NMR, Mass and analytical data. Compounds 8a, 8e, 8f and 8h exhibited good antimicrobial activity.