Background: Interleukin (IL)-23 and IL-27 are two IL-12-related cytokines which their function may dramatically influence the inflammatory response to tumor development. IL-12 and IL-27 seem to have antagonistic roles with IL-23 in tumor site. In this study, IL-23 and IL-27 mRNA expressions were analyzed in peripheral blood of patients with breast cancer and healthy volunteers using quantitative real-time PCR. Methods: Peripheral blood samples were collected from 50 women with breast cancer and 50 healthy ones. The total RNA was extracted from peripheral blood after lysis with ammonium chloride and TRizol reagent and the cDNA was synthesized. The expression of IL-23 and IL-27 gene transcripts was determined with real-time polymerase chain reaction (qRT-PCR) using Syber Green PCR Master Mix. Results: It is found that IL-23 and IL-27 transcripts had significantly higher expression in peripheral blood of patients compared with the healthy controls. The ratio of IL-23 transcript expression to IL-27 was 3.4 fold lower in the studied patients compared with the normal individuals. Conclusion: It is concluded that the over expression of IL-23 and IL-27 gene transcript in peripheral blood of breast cancer patients may be an immune response against tumor development and the inflammatory response plays a critical role in tumor development via up regulating the corresponding cytokines. However, the IL-23/IL-27 ratio may play an important role in cytokine-based immunotherapy against cancer. Further research should be carried out to assess these cytokines in a larger sample size.