The femoral vein approach is considered to be a quick and safe route for venous access. However, severe complications can occur with this access because of misplacement. Our report describes the malposition of a large-bore dialysis catheter into the left ascending lumbar vein, which led to less effective hemodiafiltration. Clinicians should be aware of possible misplacement while inserting a femoral vein catheter, especially on the left side. In some cases, the correct position in the inferior vena cava needs confirmation before using the catheter.