We report on the synthesis and biological evaluation of two series of 2,4,5-polysubstituted thiazoles comprising the acid hydrazide functionality and some derived pharmacophores known to contribute to various chemotherapeutic activities. All newly synthesized compounds were subjected to in-vitro antibacterial and antifungal screening. Of the compounds tested, 13 derivatives displayed inhibitory effect on the growth of three Gram-positive strains while they lack activity against Gram-negative bacteria. Moreover, four compounds were able to exert antifungal activity against C. albicans. Potential antibacterial and antifungal activities were linked to the thiosemicarbazide function 6a-f and those substituted with both the thioureido and thiosemicarbazide moieties 12a-f. Compounds 6f and 12f (R = 4-F-C(6)H(4)) could be considered as the most active members in this investigation with a broad spectrum of antibacterial activity against three types of Gram-positive bacteria, together with an appreciable antifungal activity against C. albicans. Compounds 6d, 6f, and 12f were twice as active as ampicillin against B. subtilis. The best antifungal activity was shown by compound 6d 50% less active than clotrimazole. 17 compounds were selected and tested for their preliminary in-vitro anticancer activity according to the current one-dose protocol of the NCI. Three cell lines, non-small cell lung cancer Hop-92, ovarian cancer IGROV1, and melanoma SK-MEL-2, exhibited some sensitivity against most of the tested compounds. Compound 12f proved to be the most active anticancer member with a broad spectrum of activity against most of the tested subpanel tumor cell lines. Consequently, 12f was carried over to be tested in the five-dose assay.