Most cases of abdominal lymphangioma are asymptomatic. However, patients may occasionally present with acute abdomen because of an intestinal obstruction or peritonitis caused by infected cysts, hemorrhaging, and/or torsion. These conditions may differ based on the location of the lymphangioma and do not always require emergency surgery. This report presents two cases of abdominal lymphangioma derived from the omentum, which required emergency surgery because of severe abdominal distension and peritonitis caused by torsion, respectively. In contrast, another case of retroperitoneal lymphangioma presented with acute abdomen and underwent elective surgery after conservative therapy for peritonitis. Elective surgery is acceptable if the symptoms are controllable under conservative therapy. However, it is important not to overlook the possible lethal complications such as intestinal and/or urological obstruction, aggressive peritonitis, and torsion of the cyst, which require emergency surgery.