The reaction of 2,3,5-trichlorobenzoic acid hydrazide with carbon disulfide and potassium hydroxide followed by treatment with hydrazine hydrate afforded 3-(2,3,5-trichlorophenyl)-4-amino-1,2,4-triazole-5-thione (6). Alternatively, this triazole was also synthesized by fusing 2,3,5-trichlorobenzoic acid with thiocarbohydrazide. Condensation of (6) with various aromatic carboxylic acids in the presence of phosphorous oxychloride or with phenacyl bromides afforded two series of fused heterocycles namely 6-(substituted aryl)-3-(2,3,5-trichlorophenyl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadizoles (7) and 6-(substituted aryl)-3-(2,3,5-trichlorophenyl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines (8), respectively. The structures of these newly synthesized compounds are characterised by elemental analysis, IR, (1)H NMR and mass spectroscopic studies. All the synthesized compounds were screened for their antimicrobial and anti-inflammatory activities. Some of the compounds exhibited promising antimicrobial and anti-inflammatory activities.