Systemic lupus erythematosus (SLE) is a chronic inflammatory disease of unknown etiology and is characterized by presence of variable pathogenic auto-antibodies and multiple organ involvement. Serositis is common in SLE, but peritoneal involvement is relatively rare. This is a case report of 28-year-old female who initially presented with abdominal pain and ascites. After ruling out many other possibilities such as liver cirrhosis, neoplasm, and infectious etiologies, we confirmed SLE with clinical features, serologic tests and radiological findings. To conclude, her abdominal pain and ascites were caused by lupus peritonitis. After administration of corticosteroid therapy, her symptoms fairly improved.