This review explores the impact of sex hormones on cerebrovascular development and the onset of neurodevelopmental disorders, focusing on autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). Proper cerebrovascular development and neurovascular unit assembly are crucial for brain growth and function, involving key pathways such as vascular endothelial growth factor (VEGF) and Wnt signaling. These pathways are essential for brain vascular growth, expansion, and blood–brain barrier (BBB) maturation. During fetal and neonatal life, cerebrovascular formation coincides with the early peak activity of the hypothalamic-pituitary-gonadal axis, suggesting a role for sex hormones in cerebrovascular development. Sex hormonal dysregulation in early development has been linked to neurodevelopmental disorders with sexually dimorphic features, such as ASD and ADHD. Both disorders show higher prevalence in men, with varying symptoms between sexes. ASD and ADHD are associated with high prenatal testosterone exposure and reduced aromatase expression, potentially explaining sex differences in prevalence and symptomatology. High estrogen levels seem to attenuate ADHD symptoms, and sex- and region-specific variations of cerebral blood flow perfusion have been reported in both conditions. The review discusses the concept of gonadal hormone interactions with brain vascular and BBB development, focusing on the modulation of VEGF and Wnt signaling. It outlines how these pathways may contribute to the underpinnings of ASD and ADHD. The authors highlight outstanding questions and potential avenues for future research, emphasizing the need to uncover sex-specific physiological and pathological aspects of brain vascular development to develop innovative therapeutic approaches for ASD, ADHD, and beyond.This review explores the impact of sex hormones on cerebrovascular development and the onset of neurodevelopmental disorders, focusing on autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). Proper cerebrovascular development and neurovascular unit assembly are crucial for brain growth and function, involving key pathways such as vascular endothelial growth factor (VEGF) and Wnt signaling. These pathways are essential for brain vascular growth, expansion, and blood–brain barrier (BBB) maturation. During fetal and neonatal life, cerebrovascular formation coincides with the early peak activity of the hypothalamic-pituitary-gonadal axis, suggesting a role for sex hormones in cerebrovascular development. Sex hormonal dysregulation in early development has been linked to neurodevelopmental disorders with sexually dimorphic features, such as ASD and ADHD. Both disorders show higher prevalence in men, with varying symptoms between sexes. ASD and ADHD are associated with high prenatal testosterone exposure and reduced aromatase expression, potentially explaining sex differences in prevalence and symptomatology. High estrogen levels seem to attenuate ADHD symptoms, and sex- and region-specific variations of cerebral blood flow perfusion have been reported in both conditions. The review discusses the concept of gonadal hormone interactions with brain vascular and BBB development, focusing on the modulation of VEGF and Wnt signaling. It outlines how these pathways may contribute to the underpinnings of ASD and ADHD. The authors highlight outstanding questions and potential avenues for future research, emphasizing the need to uncover sex-specific physiological and pathological aspects of brain vascular development to develop innovative therapeutic approaches for ASD, ADHD, and beyond.