The basic surgical treatment for avascular necrosis of the femur head is core decompression. In this report we discuss a case where the patient developed compartment syndrome after core decompression surgery with history of anticoagulant use. A 49-year-old man, who was using Coumadin 5 mg once daily due to aortic valve replacement and atrial fibrillation, had undergone core decompression surgery done due to stage 2 femur head avascular necrosis (AVN). He later developed isolated anterior thigh compartment syndrome for which fasciotomy was performed. Every surgical intervention to the extremities of patients with anticoagulant treatment should be considered high risk for compartment syndrome, even if appropriate precautions are taken. It is necessary to clinically observe for a sufficient duration to be able to identify symptoms.