h i g h l i g h t s• Chronic stress impairs the development of the adolescent brain.• Chronic stress delays the maturation of extracellular structures called perineuronal nets, which stabilize synaptic contacts on inhibitory neurons, and prefrontal cortex-associated behavior.• These negative effects of chronic stress on the prefrontal cortex can theoretically occur in humans. Critical periods of plasticity (CPPs) are defined by developmental intervals wherein neuronal circuits are most susceptible to environmental influences. The CPP of the prefrontal cortex (PFC), which controls executive functions, extends up to early adulthood and, like other cortical areas, reflects the maturation of perineuronal nets (PNNs) surrounding the cell bodies of specialized inhibitory interneurons. The aim of the present work was to evaluate the effect of chronic stress on both structure and function of the adolescent's rat PFC. We subjected P28 rats to stressful situations for 7, 15 and 35 days and evaluated the spatial distribution of histochemically-labeled PNNs in both the Medial Prefrontal Cortex (MPFC) and the Orbitofrontal Cortex (OFC) and PFC-associated behavior as well. Chronic stress affects PFC development, slowing PNN maturation in both the (MPFC) and (OFC) while negatively affecting functions associated with these areas. We speculate upon the risks of prolonged exposure to stressful environments in human adolescents and the possibility of stunted development of executive functions.