Prenatal stress induced by maternal activation of the hypothalamic-pituitary-adrenal (HPA) axis and subsequent release of glucocorticoids can profoundly affect fetal brain development. This study investigates the molecular mechanisms underlying prenatal stress in Gallus gallus domesticus by analyzing the brain proteome of embryos exposed to corticosterone. Using one of the most comprehensive proteomic analyses of the developing chicken brain to date, in which over 6,500 proteins were quantified, we identified significant myelination deficits as a key pathological feature. These results are consistent with previous research in mammalian models, highlighting the utility of Gallus gallus as a non-mammalian model for studying the effects of prenatal stress on neurodevelopment.