Severe hypothermia has a high mortality rate and necessitates aggressive warming to save lives. One of the most effective treatments for severe hypothermia is intravascular rewarming. Intravascular recuperative warming can be delivered by inserting a catheter through the cervical or femoral veins. Catheter insertion through the femoral vein is a commonly performed procedure with fewer complications than catheter insertion through the internal jugular vein. This procedure is commonly conducted by inserting a central venous catheter through the femoral vein. When a catheter is inserted through the femoral vein, a frontal abdominal radiograph is often used to confirm the position of the catheter tip. Case Report: We present the case of a 58-year-old Japanese man who had severe hypothermia. Under ultrasound guidance, a catheter was inserted through the femoral vein into the inferior vena cava for active rewarming. A frontal abdominal radiograph showed that a catheter tip appeared to be in the inferior vena cava. However, a subsequent computed tomography scan revealed that the catheter tip had been misplaced into the right ascending lumbar vein. Conclusions: Catheters may stray into the right ascending lumbar vein if they are placed through the right femoral vein. Frontal abdominal radiographs may be insufficient to confirm catheter placement.