Evidence shows that secondary metabolites of saffron can be used in the formulation of new drugs for the treatment of various human cancers. It is demonstrated that saffron crocin inhibits the proliferation of cancer cells while having no inhibition effect on the growth of normal cells. Consumption of this substance also reduces the side effects of cancer chemotherapy. Therefore, the present study was performed to investigate the effect of crocin on the proliferation and apoptosis of breast cancer cells and determine its molecular mechanism. Material & Methods: Initially, MCF7 breast cancer cells were prepared from the Pasteur Institute of Iran Cell Bank and cultured in RPMI1640 medium with FBS 10%. To determine the effect of crocin toxicity on cancer cells, treatment was conducted at different concentrations and different hours, and (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay was performed. The cell proliferation or cell apoptosis was evaluated as well. DAPI staining was performed to demonstrate cell apoptosis. After RNA extraction and cDNA preparation, the expression of an apoptosis-related gene (PTEN) and Akt pathway genes were measured by Real-time polymerase chain reaction (PCR) to determine the mechanism of the crocin effect. Findings: Results of the MTT assay showed that crocin inhibited the proliferation of MCF7 cells and induced apoptosis in these cells. In addition, real-time PCR results showed that crocin increased PTEN gene expression (P=0.041) in MCF7 breast cancer cells and significantly decreased Akt1 gene expression (P=0.038). Discussion & Conclusion: The results indicate that crocin stimulates the apoptotic cells in MCF7 breast cancer cells and can be used as a new therapeutic strategy for the treatment of breast cancer.