Objectives: Serous ovarian carcinoma (SOC) is the commonest ovarian carcinoma type with poor prognosis due to early metastasis and first presentation with advanced stage. In this work, we investigated serum level of Galac-tin-1 (Gal-1) and its tissue immunohistochemical expression in SOC patients at different stages trying to find out its significance as a diagnostic and prognostic marker. Patients and methods: The study included 95 females I-Control group: Twenty five healthy females; II-Patients group: Seventy females diagnosed as SOC at different stages; Stage I: 8 cases, Stage II: 12 cases, Stage III: 32 cases and Stage VI:18 cases. Serum Galectin-1 and CA-125 were measured by ELIZA and tissue Galectin-1 was assessed by immunohistochemistry. All patients were followed for up to 3 years after surgery. Results: Serum Gal-1 and CA-125 levels were significantly high in SOC patients compared to controls (p < 0.001). We found a direct positive statistically significant correlation between serum Gal-1 and CA125 levels (p < 0.001). Se-rum Gal-1 at cut off value > 135 ng/ml was superior to CA-125 a cut off value > 49 u/ml with sensitivity, specificity of 100%, vs 88.57, 96% for CA-125. Serum Gal-1 was significantly associated with tumor stage (p < 0.001). Immunohistochemistry showed that patients with strong Gal-1 expression had higher serum level (p = 0.002). Stromal and tumor Gal-1 expression were significantly correlated with tumor grade (p < 0.001) and stage (p = 0.001). Se-rum Gal-1, CA-125 and IHC Gal-1 expression were associated with poor survival (p < 0.001, p = 0.009 and p = 0.002) respectively. Conclusion: Serum Gal-1 and its tissue IHC expression are useful diagnostic and prognostic markers for SOC patients.