Macrophage migration-inhibitory factor (MIF) plays an important role in the pathogenesis of multiple malignancies, and its expression strongly also affects outcomes of cancer patients. The objective of this study was to determine the clinical significance of serum levels of MIF in epithelial ovarian cancer (EOC) patients. A total of 50 patients with a pathologically confirmed diagnosis of EOC were enrolled into this study. Serum MIF concentrations were determined using the solid-phase sandwich ELISA method. Age- and sex-matched 30 healthy controls were included in the analysis. Median age of patients was 56.5 years old, range 22 to 83 years. Majority of the patients had an advanced disease (International Federation of Gynecologists and Obstetricians (FIGO) stages III and IV) (90%). Baseline serum MIF levels were significantly higher than those in the healthy control group (p = 0.005). No known clinical variables including histology, grade of histology, stage of disease, debulking surgery, and serum CA 125 levels were found to be correlated with serum MIF levels (p > 0.05). Only those chemotherapy-unresponsive patients had higher serum MIF levels compared with responsive ones (p = 0.02). Patients with elevated serum MIF concentrations had significantly unfavorable overall survival compared to those with lower levels (p = 0.01). However, a serum MIF level was found to play no prognostic role for progression-free survival (p = 0.09). In conclusion, serum levels of MIF have diagnostic, predictive, and prognostic roles in EOC patients.