Intramedullary nailing of proximal femur fracture is not deprived of complications, although vascular complications are very rare and a high index of suspicion is required for timely diagnosis. This case report describes how a late-onset hematoma formation and bleeding of a small branch of the lateral circumflex femoral artery can complicate intramedullary nailing after a pertrochanteric fracture. To the best of our knowledge, this complication has never been reported and should be considered among the possible vascular complications of intramedullary nailing. Orthopedic surgeons should be aware of the vascular complications that can occur even with late-onset presentation and even from small vessels, while administration of anticoagulants is an aggravating factor. Elderly patients with proximal femur fractures are more susceptible to vascular injury due to the structure of their vessels and the vicinity of the fracture to the arterial supply of the hip.