Little is known about the effectiveness of aerobic exercise for upper limb function in patients with severe paralysis. We introduced aerobic exercise to improve upper limb function in a patient approximately three months after stroke onset. A 24-year-old woman presented with occlusion of the right internal carotid artery. We introduced high-dose self-rehabilitation for upper limb function, comprising daily three-hour self-rehabilitation sessions for 25 days, in addition to occupational therapy. After the self-rehabilitation phase, we added daily 30-minute aerobic exercise sessions for 25 days, totaling 25 sessions, on a recumbent stationary cycle ergometer. At the start of the aerobic exercise, the assessment scores were as follows: Fugl-Meyer Assessment for upper extremity (FMA-UE), 22/66; Motricity Index (MI), 48; and Motor Activity Log (MAL) for the amount of use (AOU) and quality of movement (QOM), 1.3 and 1.1, respectively. After the 25 aerobic exercise sessions, the assessment scores were as follows: FMA-UE, 32; MI, 61; and MAL for AOU and QOM, 1.6 and 1.3, respectively. The analysis using the percentage of non-overlapping corrected data showed that aerobic exercise was more effective than the self-rehabilitation sessions alone in both the FMA-UE and MI scores. Although future studies should investigate the effects of aerobic exercise in a larger number of patients, improving upper limb function may be facilitated by incorporating aerobic exercise.