Methyl-piperidino-pyrazole (MPP) is a pyrazole derivative acting as a lead estrogen receptor (ER) antagonist and has an anti-breast cancer effect. Since some benzimidazole derivatives were reported for their inhibitory activity against breast cancer, hybrids from these reported compounds (5a-c, 6a-c, 7a-c and 8a-c) were designed to develop anti-breast cancer agents. The synthesis involved 1,3-dipolar cycloaddition of nitrilimines on the benzimidazolone derivatives 2a-b and 3a-b which occurred with chemo- and regioselectivity depending on the dipole and was confirmed by an X-ray structure of 6b. In vitro biological testing of the newly prepared compounds against the 60-cell line panel showed that 5a-c and 6a-c with a partially unsaturated pyrazole ring possessed a high GI% in the T-47D breast cancer cell line with a selectivity margin against different cell lines. Five compounds were selected for apoptotic studies in T-47D cells, of which 6a arrested cells in G1 phase and caused more apoptosis than MPP. The MTT assay revealed that compound 6a has an IC