Purpose: Augmentation mammoplasty by cohesive silicone gel implant is becoming more popular nowadays. Many types of complications have been reported, such as hematoma, seroma, infection, capsular contracture and etc. But there were no report of deep vein thrombosis(DVT) after augmentation mammoplasty in Korea. The authors experienced one case of DVT after augmentation mammoplasty using a cohesive silicone gel implant. Methods: A 38-year-old woman with breast cancer underwent reconstruction by tissue expander and augmentation mammoplasty by cohesive silicone gel implant, and exchange of expander to cohesive silicone gel implant. The operation was finished without any complicating event. On 4th day after the operation, the patient complained of intermittent right lower leg pain. By doppler ultrasonography, the patient was diagnosed with acute venous thrombosis of the popliteal vein, posterior tibial vein and peroneal vein. Results: Intravenous heparinization and oral warfarin were started immediately and elastic compression stocking was applied. Intravenous heparinization was continued until INR (blood coagulation unit) reached to target levels. The patient was discharged on 11th day of operation with oral warfarin. Other complication has not been reported after 10 weeks of operation. Conclusion: To our knowledge, this is the first report of DVT after silicone implant based breast augmentation.