A series of 2-p-tolyl-1H-benzo[d]imidazole derivatives were synthesized and characterized. For finding an effective anticancer drug, which could be used in future generations, the developed heterocyclic compounds were screened in the human epithelial breast adenocarcinoma cell line (MCF-7) and human liver epithelial hepatocellular carcinoma cell line (HepG2) using the MTT assay method. Two positive control drugs were used for comparison with the compounds. The substituents on the 1- and 2-positions of the benzimidazole core had an important effect on the antiproliferation of cancerous cells. According to the results obtained, a compound, namely, 1-(4-methylbenzyl)-2-p-tolyl-1H-benzo[d]imidazole, which has electron donating groups (CH3) in the para position of a phenyl ring, showed higher cytotoxic activities compared to other compounds towards liver and breast cell lines. The compounds were found to have more cytotoxicity in HepG2 rather than MCF-7.