Corticosteroid hormones, released during stressful encounters, have profound and far-reaching effects on cognition. They are often thought to accomplish these effects primarily via glucocorticoid receptors (GR), but recent findings from rodent and human studies argue for an additional, critical role of the mineralocorticoid receptor (MR) in cognitive changes in response to stress. We propose that the MR initiates rapid changes in the recruitment of specific neural systems, inducing a shift towards cognitively less-demanding processing and allowing a quick and adequate response to the situation. In combination with slower and longer-lasting actions mediated by GR, this shift leads to optimal coping with the ongoing stressful event. Adaptive cognitive changes under stress require the brain MR for corticosteroids and its interaction with other neuromodulators released in response to stress, such as catecholamines.Under stress, the MR induces a rapid shift from 'cognitive' systems based at the hippocampus and, most likely, the prefrontal cortex, towards less-demanding 'habit' systems depending on the amygdala and the dorsal striatum. This shift is reflected in distinct changes in neural activity and connectivity within and between these brain circuits.Although this MR-dependent shift is often beneficial and promotes coping during acute stress, it might come at the cost of less access to flexible cognitive processes depending on the hippocampus and other regions involved in more reflective processing, such as the prefrontal cortex.