Triple-negative breast cancer (TNBC) is the most metastatic subtype of breast cancer and cannot be controlled with any standard-of-care therapy. However, various studies have recommended medicinal plants as complementary treatments for cancer. In particular, crocin, the main bioactive carotenoid of saffron, has exhibited anticancer effects on primary tumors. This research, for the first time, investigated the antimetastatic potency of crocin on murine model of metastatic TNBC and its effect on the Wnt/β-catenin pathway. To induce tumors, 4T1 cells were injected to female BALB/c mice. Measurement of biochemical markers showed nontoxicity of crocin. The crocin-treated mice possessed more weight, higher survival rates, and smaller tumors. Histological examination detected no metastatic deposits in their livers and lungs. Also, downregulation of the expression of Wnt/β-catenin target genes in tumors and lungs was observed compared to the untreated group. Our findings suggest crocin as a promising complementary antimetastatic herbal medicine for treatment of TNBC.