<h3>Research Objectives</h3> To investigate effects of aerobic exercise training in persons with TBI-related memory impairment. <h3>Design</h3> Single-blinded randomized controlled trial. <h3>Setting</h3> Kessler Foundation. <h3>Participants</h3> Five participants completed the trial. All were right handed, suffered a severe TBI at least 10 years ago, were physically inactive, and were prescreened for significant memory impairment. <h3>Interventions</h3> Participants were randomly assigned to either 12-weeks of supervised moderate intensity (60% peak watts) aerobic cycling exercise training or 12-weeks of supervised stretching-and-toning as an active control condition. Both conditions took place 3x/week for 30 mins/session. <h3>Main Outcome Measures</h3> Pre- and post-intervention measures included a battery of neuropsychological assessments of memory and processing speed and structural neuroimaging (MRI), administered by treatment-blinded assessors. <h3>Results</h3> Based on effect size estimates, the exercise group demonstrated substantially greater improvements in auditory verbal learning (RAVLT) (d=1.54), and larger increases in volumes of the left hippocampus (d=1.49), left cerebellar cortex (d=0.95), and right cerebellar cortex (d=1.40). There were large intervention effects favoring the exercise condition on processing speed (SDMT) (d=1.58) and volume of the right thalamus (d=1.44). <h3>Conclusions</h3> Pilot data provide important proof-of-concept suggesting that a 12-week, moderate intensity, aerobic cycling exercise training program may specifically improve memory and more generally improve processing speed in those with TBI and impaired memory. <h3>Author(s) Disclosures</h3> The authors have no conflicts of interest to disclose.