Kinefelter syndrome (KS) is a common genetic disorder caused by one or more supernumerary X chromosomes. KS poses an increased risk for venous thromboembolic events such as deep venous thrombosis and pulmonary embolism. Klinefelter syndrome is prone to hypercoagulability due to hormonal imbalance and one or more inherited thrombophilic factors. Therefore, patients with KS having a medical history of venous thromboembolism require chest computed tomographic (CT) images and oral anticoagulation therapy for a period of at least six months. A 21 year old, male patient diagnosed with Klinefelter syndrome was presented to the emergency department of our hospital with primary complaints of left lower extremity pain lasting for 2 months. Deep venous thromboembosis (DVT) was diagnosed via venous doppler ultrasound and pulmonary thromboembolism in his chest CT images. Following anticoagulation treatment, his symptoms recovered. An endocrinologic test should be ordered in patients having klinefelter syndrome with a medical or familial history of venous thromboembolism as well as additional assessment of innate or acquired thrombophilia should be made.