Neopterin is a useful indicator of the activation state of the cellular immune system, and an elevated level predicts prognosis in different types of tumors. The aim of this study was to evaluate serum neopterin levels if it is viable predictor for prognosis in breast carcinoma patients. Serum neopterin was investigated in 56 breast carcinoma patients, 16 patients with benign breast lesions and 16 healthy women as controls. Neopterin was measured by ELISA (Enzyme-linked immunosorbent assay). The clinicopathological parameters were determined by reviewing both medical charts and pathological records. All patients had been followed-up until September 2009 or death.The mean serum neopterin concentrations were 8.5 ± 5.2 nmol/L in patients with breast carcinoma, 6.5±3.1 nmol/L in patients with benign breast lesion and 8.1 ± 1.9 nmol/L in healthy volunteers (p>0.05). Elevated neopterin levels were significantly correlated with age, elevated serum CRP level, advanced stage and presence of the distant metastases (p<0.05). Overall survival was significantly shorter in patients with a serum neopterin level >10 nmol/L than patients with neopterin <10 nmol/L level (56 months vs. 76 months, p=0.011). Increased preoperative serum neopterin concentrations are associated with a poor prognosis in patients with breast carcinoma.