Background: Polyamine metabolism has a critical role in cancer initiation and progression. The abnormal overexpression of the ornithine decarboxylase (ODC1) enzyme gene could be a characteristic of cancer cells. Objectives: The current study evaluated the cytotoxic effects of Rheum khorasanicum extract in three different solvents, including distilled water, ethanol, and n-hexane, on the MCF-7 breast cancer cell line and assessed the expression level of the ODC1 gene upon the abovementioned treatments. Methods: We cultured MCF-7 cancer cells in complete cell culture media and subsequently subjected them to increasing concentrations (0 - 200 μg/mL) of the extract. The cytotoxic activity of the extract was investigated using an MTT assay. The quantitative analysis of ODC1 gene expression was performed using real-time PCR. Results: The cell viability was significantly decreased in concentration- and time-dependent manners. The mRNA expression of the ODC1 gene declined gradually with the increasing concentrations of extracts. Conclusions: Our findings indicated that R. khorasanicum extract could potentially influence ODC1 gene expression in breast cancer cells and exert inhibitory effects on cancer cell proliferation.