This study aimed to synthesize the nickel (Ni) doped cobalt ferrite (CFO) nanoparticles and to determine its anticancer effect on breast cancer MCF‐7 cells. The various concentrations of Ni (0.2%, 0.4%, 0.6%, 0.8%, and 1%) doped CFO nanoparticles were synthesized using Coriandrum sativum extracts by precipitation technique. The synthesized Ni‐CFO was characterized by X‐ray diffraction, Fourier transform infrared spectroscopic, transmission electron microscopy, and vibrating sample magnetometer analyses. The results show that 0.8% Ni‐CFO nanoparticles showed good magnetic properties and antioxidant activity than other concentrations of Ni‐CFO. The results showed that the administration of 0.8% Ni‐CFO nanoparticles promoted apoptosis, and reduced cell adhesion and migration of MCF‐7 cells, as demonstrated by increased lipid peroxidation, decreased antioxidant levels such as superoxide dismutase, catalase, and glutathione peroxidase, and increased formation of reactive oxygen species. Moreover, administration of 0.8% Ni‐CFO nanoparticles decreased the Bcl‐2 expression while activating the expression of p53, Bax, and cleaved caspase 3, 8 and 9 protein expression. Notably, 0.8% Ni‐CFO treatment reduced phospho‐PI3K, phospho‐Akt, and phospho‐mTOR expression levels. As a result, via altering apoptotic related proteins, 0.8% Ni‐CFO induced cell death. Therefore, the 0.8% Ni‐CFO could be utilized to treat breast cancer.