Gestational diabetes mellitus (GDM) with intrauterine hyperglycemia induces a series of changes in the placenta, which have adverse effects on both the mother and fetus. Although some studies have examined these changes in the placenta, the differences resulting from fetal sex remain unelucidated. In this study, we established an intrauterine hyperglycemic model using ICR mice. We collected placental specimens before birth for histological observation using Hematoxylin and Eosin (HE) staining, along with Tandem Mass Tag (TMT) labeled proteomic analysis which was stratified by sex. In both male and female fetuses of the GDM group, body weight and placental weight were significantly lower compared to the control group. Additionally, the placenta-to-body weight ratio was higher, suggesting potential placental insufficiency. Histological analysis revealed smaller sizes and reduced thickness of the junctional zone and labyrinth in diabetic placentas at E18.5, along with ectopic accumulation of spongiotrophoblasts in the labyrinth. When the analysis was not segregated by sex, the GDM group showed 208 upregulated and 225 downregulated proteins in the placenta, primarily within the extracellular matrix and mitochondria. Altered biological processes included cholesterol metabolism and oxidative stress responses. After stratifying by sex, the male subgroup displayed 209 upregulated and 111 downregulated proteins, while the female subgroup exhibited 97 upregulated and 75 downregulated proteins. Among these, 64 differentially expressed proteins showed consistent trends across both sexes, primarily enriched in the JAK-STAT signaling pathway, complement and coagulation cascades, and metabolism-related modifications. The male subgroup showed a heightened tendency for immune-related pathway alterations, whereas the female subgroup manifested changes in branched-chain amino acid metabolism. The intrauterine hyperglycemic environment affects both placental morphology and proteomics, leading to shifts in energy metabolism, oxidative stress responses, and immune processes. Our study suggests that the observed differences in placental protein expression specific to each sex may provide an explanation for the varying impacts of GDM on offspring.