Acquired von Willebrand syndrome (AVWS) is a rare clinical entity presenting with heterogeneous hemorrhagic manifestations, although some subsets of patients with AVWS may be asymptomatic until they are exposed to major trauma, an invasive procedure, or surgery. We herein report one such case in a 73-year-old male patient with nephrotic syndrome with a prolonged active partial thromboplastin time. We initially did not deal with this distinct abnormal clotting profile seriously, but persistent bleeding after a retroperitoneoscopic-assisted renal biopsy that allowed us to ascribe his nephrotic syndrome to membranous nephropathy fortuitously led to the discovery of concurrent AVWS. We feel that an accurate and prompt diagnosis as well as awareness of the disease remain a challenge for physicians and therefore strongly recommend the further accumulation of experiences similar to our own in a prospective manner. This report underscores the pitfalls associated with determining the bleeding risk, including an insufficient assessment and improper weighting of an abnormal clotting profile prior to the invasive procedure. Several management concerns that emerged in the current case are also discussed.