A series of novel N-(5-benzyl-4-(tert-butyl) thiazol-2-yl)-2-(piperazin-1-yl)acetamides were designed, synthesized and evaluated for their antitumor activities in vitro. The structures of the synthesized compounds were characterized by<sup>1</sup>H NMR,<sup>13</sup>C NMR and elemental analysis. In general, compounds 5a, 5c and 6a showed potent antiproliferative activity against HeLa (human cervical cancer) and A549 (human lung cancer) cell lines. Compound 6a, with the best inhibitory activity against HeLa cells (IC<inf>50</inf> = 1.6 ± 0.8 μM), was selected to investigate the induced changes of cell morphology in the HeLa cell line by means of acridine orange (AO)/ethidium bromide (EB) double staining and cell cycle analysis using flow cytometry. The results indicated that compound 6a could induce cell apoptosis and cause G1-phase arrest in the cell division cycle. ©2017, Springer Science+Business Media Dordrecht.