A series of substituted 2-phenylthiazole-4-carboxamide derivatives were synthesized as potential cytotoxic agents and evaluated against three human cancer cell lines including T47D (Breast cancer), Caco-2 (Colorectal cancer) and HT-29 (Colon cancer). The SAR of the arylacetamido pendent connected to the para-position of 2-phenylthiazole were explored. It was found that substitution at the 4-position by a methoxy group led to improvement of activity against Caco-2 cells while 2-methoxy substituent could maintain the high activity against HT-29 and T47D cell lines. Also, 3-fluoro analog showed good cytotoxic activity profile against all cell lines with IC(50) values less than 10 μg/mL.