Introduction: Despite high rates of mortality and morbidity due to preterm delivery, none of the diagnostic and biochemical tests could help to accurately identify the cases at risk of preterm delivery. Objectives: Since ferritin is an acute phase reactant, this study aimed to evaluate serum ferritin levels in women with preterm and term delivery. Methods: This study was conducted on 150 women with preterm delivery (50 cases in each of the groups 24-30, 30-34, and 34-37 weeks of pregnancy), 150 women with term delivery, and 150 pregnant women who were between 24-37 weeks of pregnancy (same as preterm delivery groups). Results: The mean ferritin level in all preterm groups was significantly higher than that in the term group, but there was no difference among the preterm groups. In addition, ferritin level in each preterm group was significantly higher than those in the normal pregnancy group at the same gestational age. In preterm deliveries, ferritin levels were significantly higher in cases with prelabor rupture of membranes (PROM) or with a prolonged leakage (longer than 12 hours). In addition, in patients with PROM or prolonged leakage, ferritin levels were significantly higher in preterm deliveries than in term deliveries. A ferritin level of 37.5 ng/mL recognized as the best cut-off for preterm delivery, as compared with term delivery, and its sensitivity, specificity, and diagnostic accuracy was 78.7%, 68.7%, and 73.6%, respectively. Conclusion: The findings of the present study showed that serum ferritin level can be used to find patients at risk of preterm delivery.