Pulmonary embolism (PE) is an extremely common and highly lethal condition. A good clinician actively seeks the diagnosis as soon as any suspicion of PE is warranted, because prompt diagnosis and treatment can dramatically reduce the mortality and morbidity of the disease. Defecation syncope is a rare form of syncope and pulmonary embolism has not yet been included in the differential diagnosis of defecation syncope or defecation associated sudden death. Here, we presented a 72-year-old female who suffered from acute diarrhea, which was followed by defecation syncope. After a series of studies, including an electrocardiogram, a bedside echo study and computed tomography of the chest, pulmonary embolism was diagnosed and treated successfully.