In young adolescent girls, anorexia nervosa is a significant cause of weight loss, and hospital admissions among children and adolescents. Anorexia nervosa is a life-threatening disorder, with about one-third of deaths caused by cardiac complications. A high rate of pericardial effusion has been recently reported in patients with anorexia nervosa, although relatively few cases require pericardiocentesis. Here, we describe three patients with anorexia nervosa who were diagnosed with large pericardial effusions. To prevent cardiac tamponade, pericardiocentesis was performed in two girls.