Interleukins (ILs) are known to play a fundamental role in cancer. We investigated the serum levels of IL-8 and IL-12, in breast cancer patients, and their relationship with the prognostic parameters and therapy. Forty-eight patients with pathologically verified breast carcinoma and 21 healthy controls were enrolled into the study. Serum samples were obtained at baseline and after two cycles of chemotherapy. Serum IL-8 and IL-12 levels were determined using enzyme-linked immunosorbent assay (ELISA). There was no significant difference in the baseline serum L-8 and IL-12 levels between breast cancer patients and healthy controls (p = 0.365 and p = 0.871, respectively), no significant correlation between the prognostic parameters and the serum IL-8, IL-12 levels. However, in the subgroup consisting of metastatic breast cancer patients, baseline serum IL-8 levels were significantly higher compared with non-metastatic disease (p = 0.047). Anthracycline-based chemotherapy and the addition of taxane did not change the levels of both serum IL-8 and IL-12. Serum IL-8 level may be useful in determining metastatic breast cancer. Larger studies are needed to confirm this finding.