Introduction: Gestational diabetes mellitus (GDM), one the most endocrine complication of pregnancy, is more prevalent in pregnant mothers who conceived by assisted reproduction technology (ART). The association between pre-pregnancy body mass index (BMI) with GDM was reported. Screening for gestational diabetes mellitus (GDM) is usually performed at 24–28 weeks of gestation. However, almost 10% of GDM mother was detected at first trimester. The purpose of this study was to assess diagnostic value of pre-pregnancy body mass index to detect GDM in ART singleton pregnancy population. Methods: This case-control study was performed among 264 singleton pregnant women conceived through ART referring to Royan institute, Tehran, Iran. GDM was detected by a one-step OGTT at 24th – 28th weeks of gestation. Pre-gravid weight and height was measured before ART cycles. Body mass index (BMI) was calculated. Receiver operating characteristic (ROC) curve analysis was performed to assess the value of pre-gravid BMI in women under ART treatment. The sensitivity and specificity of BMI to detect GDM were determined. p < 0.05 was considered significant. Results: Two hundred sixty four women consisted of 135 ART subjects with GDM and 129 ART subjects without GDM was enrolled. Women who developed GDM had significantly higher age, BMI, history of diabetes in first degree and history of PCOS compared with non-GDM group, (p < 0.05). The rate of overweight and obesity was higher in GDM group. The mean pre-gravid BMI (27.4 kg/m2 vs. 24.6 kg/m2, <0.001) was significantly higher in GDM group. Pre-gravid BMI at a cut-off value of 25.4 mg/dl showed a sensitivity of 70.4%, (CI: 61.91-77.92) and a specificity of 61.3%, (CI: 52.27-69.69) with overall accuracy 65.9% for GDM prediction.