A series of novel 1,2,3-thiadiazolo-5-carboxylic acid hydrazide Schiff's bases 4a–4r were prepared starting from ethyl-4,4,4-trifluoroacetoacetate and ethyl carbazate in four steps. All the compounds were screened for antibacterial activity against various bacterial strains at 150 lg/ml concentration and found no activity. Similarly, all the compounds were screened for antifungal activity against various fungal strains at 100 and 150 lg/ml concentrations. Compounds 4a, 4m, and 4q found to show moderate activity against Candida albicans. Further, compounds were evaluated for cytotoxic activity against breast carcinoma cells MDA-MB 231 (aggressive), MCF-7 (non-aggressive) using doxorubicin as standard. Compound 4n was found to show 25.39 % cell viability against MDA-MB 231 and 63.60 % cell viability against MCF-7 cells.