This pilot study explored the effect of moderate-intensity exercise on factor VIII (FVIII) activity and global hemostatic status of the children with severe hemophilia A. Eleven children aged 6 to 15 years with severe hemophilia A participated in a moderate-intensity exercise test by using Recumbent Cross Trainer (NuStep, T5XR) for at least 10 min after reaching the target heart rate or until volitional exhaustion within a safety framework. Blood samples were collected pre and postexercise for plasma FVIII: C and thromboelastography (TEG) parameters and coagulation index. The average duration of exercise was 11.8 min (10–13 min). There was no report on bleeding events or adverse symptoms requiring termination of the exercise test. The average FVIII activity of the 11 children was 0.66 (0.5–0.8) IU/dl before and 0.93 (0.5–2.3) IU/dl after exercise. The increase of FVIII in the 11 children as a group was not statistically significant (P = 0.052). There were significant changes of TEG measurements, with shortening of R (P < 0.05), and increase in K decrease (P < 0.05), alpha angle (P < 0.05), maximum amplitude (P < 0.05), and coagulation index (P < 0.01). Among the 11 children, the relative coagulation index increase after exercise was greater than 50% in seven (63.6%), less than 20% in three (27.3%), and less than 10% in one (9.1%). TEG analysis showed that the global hemostatic function for the children with severe hemophilia A can be enhanced after moderate-intensity exercise.