Marfan syndrome is an inherited disorder of connective tissue involving various organs. There is no data in the literature regarding balance disturbance or fall risk for sportsmen with Marfan syndrome. In this case report, we present a 24-year-old male professional athlete with Marfan syndrome who has been playing basketball for a period of 10 years, of which, the last three years being in the premier league. A high risk of falls and poor postural performance was detected in the patient during follow-up performed annually in athletes, including locomotor system examination, isokinetic evaluation of muscular performance using isokinetic machine and fall index, and postural performance assessment using static posturography. Due to the strong correlation between balance and muscle strength, imbalance is not an expected situation in athletes. Sports medicine physicians and trainers must pay attention to take necessary precautions in athletes with Marfan syndrome. Data for fall index can help to re-arrange exercise program and to prevent traumas that can occur following a fall. Turk J Phys Med Rehab 2011;57 Suppl 2: 354-7.