Breast cancer is the most common malignancy predominantly affecting women. To date, numerous numbers of studies were reported novel genetic contributors with diagnostic, prognostic, and therapeutic potential for the breast carcinogenesis. However, the role of urotensin-II in breast carcinogenesis has not been elucidated yet. Urotensin-II is a somatostatin-like cyclic tiny peptide identified by its potent vasoconstrictor activity. Soon after its discovery, its involvement in many disease states as well as its expression in various tissues including the tumors have been demonstrated. Moreover, there is strong evidence that suggest urotensin-II as the significant contributor of angiogenesis as well as cell proliferation and tumor biology. In this study, enzyme-linked immunosorbent assay (ELISA) and restriction fragment length polymorphism analysis were used to evaluate plasma levels of urotensin-II and Thr21Met and Ser89Asn polymorphisms of UTS2 gene in breast cancer patients. In the present case-control study, we noticed a significant decrease in the levels of urotensin-II protein in the plasma of the breast cancer patients (p < 0.05). Also, Thr21Met polymorphism in the UTS2 gene was associated with the risk of developing breast cancer (p < 0.0001), whereas the genotype frequency of Ser89Asn was found to be similar in patients and controls (p > 0.05). In addition, we demonstrated the gradual decreasing of urotensin-II protein levels from TT and TM to MM genotypes. In conclusion, these results strongly suggest that urotensin-II could contribute to breast carcinogenesis and Thr21Met polymorphism can be an important risk factor in developing breast tumors.