Background and objective. In spite of the challenges, engaging in exercise programs very early after stroke may positively influence aerobic capacity and stroke-related outcomes, including walking ability. The objective of this study was to evaluate the feasibility of adding aerobic cycle ergometer training to conventional rehabilitation early after stroke and to determine effects on aerobic capacity, walking ability, and health-related quality of life. Methods. A prospective matched control design was used. All participants performed a graded maximal exercise test on a semi-recumbent cycle ergometer, spatiotemporal gait assessments, 6-Minute Walk Test, and Stroke Impact Scale. The Exercise group added 30 minutes of aerobic cycle ergometry to conventional inpatient rehabilitation 3 days/week until discharge; the Control group received conventional rehabilitation only. Results. All Exercise participants (n = 23) completed the training without adverse effects. In the 18 matched pairs, both groups demonstrated improvements over time with a trend toward greater aerobic benefit in the Exercise group with 13% and 23% increases in peak VO2 and work rate respectively, compared to 8% and 16% in the Control group (group-time interaction P = .71 and .62). A similar trend toward improved 6-Minute Walk Test distance (Exercise 53% vs Controls 23%, P = .23) was observed. Conclusion. Early aerobic training can be safely implemented without deleterious effects on stroke rehabilitation. A trend toward greater improvement in aerobic capacity and walking capacity suggests that such training may have an early beneficial effect and should be considered for inclusion in rehabilitation programs.