Post-trial pharmacological activation of the noradrenergic system can facilitate memory consolidation. Because exercise activates the locus coeruleus and increases brain norepinephrine release, we hypothesized that post-trial exercise could function as a natural stimulus to enhance memory consolidation. We investigated this in amnestic mild cognitive impairment (aMCI) and cognitively normal elderly individuals by examining the effects of an acute bout of post-learning, aerobic exercise (6 minutes at 70% VO2 max on a stationary bicycle) on memory for some emotional images. Exercise significantly elevated endogenous norepinephrine (measured via the biomarker, salivary alpha-amylase) in both aMCI patients and controls. Additionally, exercise retrogradely enhanced memory in both aMCI patients and controls. Acute exercise that activates the noradrenergic system may serve as a beneficial, natural, and practical therapeutic intervention for cognitive decline in the aging population.