In this study, twenty-five (25) substituted aryl thiazoles (SAT) 1–25 were synthesized, and their in vitro cytotoxicity was evaluated against four cancer cell lines, MCF-7 (ER+ve breast), MDA-MB-231 (ER−ve breast), HCT116 (colorectal) and HeLa (cervical). The activity was compared with the standard anticancer drug doxorubicin (IC50=1.56±0.05μM). Among them, compounds 1, 4–8, and 19 were found to be toxic to all four cancer cell lines (IC50 values 5.37±0.56–46.72±1.80μM). Compound 20 was selectively active against MCF7 breast cancer cells with IC50 of 40.21±4.15μM, whereas compound 19 was active against MCF7 and HeLa cells with IC50 of 46.72±1.8, and 19.86±0.11μM, respectively. These results suggest that substituted aryl thiazoles 1 and 4 deserve to be further investigated in vivo as anticancer leads.