Background and Objective: Glucose Challenge Test (GCT) is done for pregnant women during the week 24-28 of gestation to screen gestational diabetes. In patients with abnormal GCT, a glucose tolerance test (GTT) is performed, and if GTT is impaired, the patient is diagnosed with gestational diabetes. There is some evidence suggesting that abnormal GCT alone is associated with adverse pregnancy outcomes. The aim of this study was to determine the pregnancy outcomes in patients with abnormal GCTs but normal GTT scores. Materials and Methods: In this cohort study, GCT was carried out on 190 pregnant women during the 24th to 28th weeks of gestation. Ninety-five pregnant women with abnormal GCT and normal GTT (study group) and 95 cases with normal GCT (control group) scores entered the study and were compared regarding adverse pregnancy outcomes. Results: The average birth weight in the study and control groups were3397±524gr and 3234±384 gr respectively (P=0.015). Fourteen neonates (14.7%) in the study group and 4(4.2%) in the control group had macrosomia (P=0.013). Frequency of preterm labor was 8 (8.4%) in the cases and 1 (1%) in the controls (P=0.03). Frequency of preeclampsia was 8 (8.4%) in the cases and 1 (1%) in the controls (P=0.03). There was positive family history of diabetes mellitus in 20 (21%) of the cases and 1 (1%) in the controls (P<0.001). Mean BMI changes was 5+1.7 in the study group and 4.3+4.3 in the controls (P<0.004). Conclusion: The prevalence of macrosomia, preterm labor, preeclampsia, family history of diabetes, increasing maternal BMI, and average birth weight were all higher in the pregnant women with abnormal GCT. Thus, due to the high incidence of some unfavorable outcomes, careful follow up women with abnormal GCT but normal GTT appears necessary during pregnancy.