Atraumatic splenic rupture (ASR) in a patient undergoing peritoneal dialysis (PD) is uncommon, but can be life-threatening. According to recent systematic reviews, the major causes of ASR are 1) neoplastic (30.3%), 2) infectious (27.3%), 3) non-in-fectious inflammatory (20.0%), 4) iatrogenic (9.2%), 5) mechanical (6.8%), and 6) idiopathic (6.4%). It is diagnosed by imaging studies, most commonly ultrasonography and computed tomography (CT). Due to its rarity, the early diagnosis of ASR is difficult, and no standard treatment has been described. Here, we report a case of idiopathic ASR in a patient undergoing PD. The diagnosis was established by abdominal CT scan, and splenectomy was performed. Thus, hemoperitoneum in a PD patient should raise suspi-cion of ASR. Early diagnosis and appropriate treatment will lead to a better outcome. (Korean J Med 2019;94:526-529)