Background: Gestational diabetes mellitus (GDM) is associated with significant maternal and fetal complications, including preterm delivery, macrosomia, and neonatal hypoglycemia. Elevated serum ferritin levels, a marker of inflammation and oxidative stress, may exacerbate these risks. This study was aims to determine if serum ferritin elevation is a marker of adverse maternal and fetal outcome in pregnancies complicated by GDM. Method: A case control study was conducted in the Department of Obstetrics and Gynecology, Dhaka Medical College, Dhaka from September 2020 to August 2021. 42 pregnant women at 2nd 3rd trimester attended for antenatal care diagnosed as GDM was selected as cases and 42 non-diabetic pregnant women matching with cases by age and gestational age was selected as control are included this study. GDM was diagnosed by oral glucose tolerance test (OGTT). The serum ferritin level of these patients was measured. Results: Elevated serum ferritin was significantly associated with GDM (p<0.05). GDM women had higher rates of obesity (p=0.005), preterm delivery (30.9% vs. 16.6%) and term delivery was less in case group (69.05%) than controls (83.33%) . In neonates of GDM mothers macrosomia rates were 26.19% in case group and 14.3% in control group. Hypoglycemia was 16.6%, respiratory distress 11.9% and NICU admissions 21.4% (p<0.05 vs controls). Conclusion: Elevated serum ferritin is a strong predictor of adverse maternal and neonatal outcomes in GDM pregnancies. These findings suggest that ferritin could serve as a biomarker for identifying high-risk pregnancies. Incorporating ferritin screening into antenatal care may facilitate early risk stratification and targeted interventions.