A new series of N-[4-(2-substituted hydrazine-1-carbonyl)thiazole-2-yl]acetamides was synthesized and evaluated in vitro against six human cell lines as antitumor agents. Compounds 20, 21 and 22 showed remarkable inhibition to HeLa (IC<sub>50</sub> values of 1.67, 3.81, 7.92 µM) and MCF-7 (IC<sub>50</sub> values of 4.87, 5.81, 8.36 µM, respectively) cell growth with high selectivity indices and safety profiles. Compound 20 showed significant decreases in both tumor volume and body weight gain compared to vehicle control, in the solid tumor animal model of Ehrlich ascites carcinoma (EAC) with recovered caspase-3 immuno-expression. Flow cytometry cell analysis showed that 20 exerts anti-proliferative activity in mutant Hela and MCF-7 cell lines through arresting the cell growth at the G1/S phase producing cell death via apoptosis rather than necrosis. To explain the antitumor mode of action of the most active compounds, EGFR-TK and DHFR inhibition assays were carried out. Compound 21 conveyed dual EGFR/DHFR inhibition with IC<sub>50</sub> 0.143 (EGFR) and 0.159 (DHFR) µM. Compound 20 showed DHFR inhibition with IC<sub>50</sub> 0.262 µM. Compound 22 exhibited the best EGFR inhibitory efficacy with IC<sub>50</sub> 0.131 µM. Molecular modelling study revealed that 21 and 22 have binding interactions with EGFR amino acid residues Lys745 and Asp855. Compounds 20 and 21 showed affinity toward DHFR amino acid residues Asn64, Ser59 and Phe31. The ADMET profile and Lipinski's rule of five calculated for these compounds were acceptable. Compounds 20, 21 and 22 could be regarded as promising prototype antitumor agents for further optimization.