Percutaneous declotting of a thrombosed fistula or graft is standard of care and is a safe procedure. Subclinical pulmonary embolism (PE) during this procedure occurs commonly, but symptomatic PE is extremely rare. The authors report a case of declotting-associated massive PE with cardiopulmonary arrest and successful resuscitation. The patient developed a new right-axis deviation and right-bundle branch block. Diagnosis of PE was confirmed with a computed tomography (CT) angiogram, and the patient received tissue plasminogen activator (tPA) and heparin. She required norepinephrine and dobutamine temporarily and was subsequently extubated successfully. Massive PE is a very rare complication of this procedure. Given the grave outcome, the clinical signs and symptoms should be recognized immediately and treatment instituted early.