Glucocorticoids (GCs), produced by the stress-responsive hypothalamic–pituitary–adrenal axis, are well recognized for their regulatory role in peripheral metabolism. GCs are also known to regulate various brain functions, with well-described effects on human cognition. Increased GC exposure in humans—including exposure to the endogenous GC, cortisol—at levels associated with stress, decreases memory and learning function. These results extend evidence from in vitro studies of synaptic and cell function and evidence from animals indicating the GCs can regulate substrates of memory function. While considerable evidence details these effects in adult humans and animals, relatively less is know about the effect of GCs on cognitive function in children and older adults. Investigators have suggested that children, particularly preschool-aged children, may be vulnerable to adverse consequences of increased GC secretion resulting from stress and neuropsychiatric diseases such as depression. Adverse GC effects on memory substrates and memory function in the adult have also fostered concern that age-related changes, including changes in GC receptors and changes in circulating cortisol levels, could lead to age-related increases in the adverse effect of GCs on brain function. Investigators have reported an association between age-related increases in cortisol levels and age-related memory decline, but this association may or may not be due to a direct effect of cortisol on memory substrates. A number of possible treatment approaches to prevent or remediate adverse GC-induced effects are under development. In general, the use of safe and effective agents for blocking adverse GC effects on brain functions including memory may offer benefits to individuals suffering acute and chronic stressors and could prevent brain changes relevant to stress, aging, and stress-related neuropsychiatric diseases.