Crocin is the main biologically active carotenoid of saffron, which is generally derived from the dried stigma of Crocus sativus L. Crocin has considerable pharmaceutical activities including antioxidant, anti-inflammatory, hepatoprotective, hypotensive, antidiabetic and anticancer effects. Gastric cancer is the fifth most common malignancy and the fourth leading cause of cancer-associated death worldwide. The aim of current study was to investigate toxic effects of crocin, alone and in combination with radiation, on human gastric cancer cells for the first time. To do so, MKN-45 cells were treated with 2 mM crocin for 72 h. Meanwhile, cells were also treated with 2 mM of crocin for 24 h and then exposed to 600 cGy X-ray followed by 48 h recovery. Cell viability was determined after both approaches by alamarBlue assay. Results revealed that 2 mM crocin decreased cell density and 2 mM crocin + 600 cGy X-ray decreased cell density and changed the morphology of MKN-45 cells. Calculating the viability of cells also indicated that 64% of cells were alive after 7 h treatment with 2 mM crocin, while this amount was decreased down to 43.2% upon combination of 2 mM crocin + 600 cGy X-ray treatment. Further investigation on other human gastric adenocarcinoma cell lines is recommended to better evaluate combinatorial effects of crocin and radiation in vitro.