Gestational diabetes mellitus (GDM) represents a common carbohydrate metabolism disorder during pregnancy. The objective of this study was to evaluate the expression levels of mitofusin 2 (MFN2) expression in placentae of GDM patients compared to that in the placental tissues from normal uncomplicated pregnancies. A total of 70 subjects were enrolled from September 2014 to June 2016, including 42 patients with GDM (the GDM group) and 28 normal uncomplicated pregnancies (the control group). Immunohistochemical staining and qRT-PCR were used for the detection of the expression levels and distribution of MFN2 in the placentae of GDM patients and normal controls. Kolmogorov–Smirnov test was used for statistical analysis. P < 0.05 and P < 0.01 were used for assessing statistical significance. The baseline characteristics were comparable in both groups. The 1-h and 2-h postprandial glucose levels (PPG) were 7.94±1.26 versus 6.88±0.51 mmol/L and 7.01±1.34 versus 6.14±0.63 mmol/L, respectively,for the GDM group and the control group (P < 0.05). The relative expression levels of MFN2 mRNA were 0.982±1.242 for GDM and 1.257 ± 0.815 for control, respectively, with significant between group difference (P < 0.01). Immunohistochemical staining analysis showed that MFN2 was mostly distributed in the cytoplasm of syncytiotrophoblasts under optical microscopy. Additionally,about 50% of samples of the GDM group were within the intensity of moderate staining of MFN2 and more than 50% of patients in the control group were within the intensity of strong staining of MFN2. The expression levels of MFN2 in GDM placentae was significantly lower compared to that of placentae from normal uncomplicated pregnancies.