Maternal obesity is increasingly prevalent and is associated with elevated morbidity and mortality rates in both mothers and children. As the interface between the mother and fetus, the placenta has mediates the impact of the maternal environment on fetal development. Most of the literature data on the effects of maternal obesity on placental functions do not exclude potential confounding factors like metabolic diseases (e.g. gestational diabetes). Moreover, it is now clear that the placental response to maternal environment depends on the fetal sex. In this context, we reviewed how maternal obesity (in the absence of gestational diabetes) affects the human placenta in terms of (i) endocrine function, (ii) morphological characteristics, (iii) nutrient exchanges and metabolism, (iv) inflammatory/immune status, (v) oxidative stress, and (vi) transcriptome, with a focus on fetal sex specificities. A better understanding of sex-specific placental responses to maternal obesity is crucial for improving pregnancy outcomes and the health of mothers and children.