Autoimmune hemolytic anemia (AIHA) is described by destruction of Red Blood Cells (RBCs) as a result of binding of antibodies to red blood cell surface antigens. White blood cells are usually normal and hyperleukocytosis is rare. The most common microorganism that has been associated with these hemolytic processes is Mycoplasma pneumoniae. We presented a case study, a 4-year-old boy child who was diagnosed AIHA by warm antibody testing with high leukocyte count. The patient was treated with methylprednisolone, intravenous immunoglobulin and clarithromycin. During treatment, the leukocytosis became normal. The clinical condition and vital signs improved. The purpose of this study was to highlight hyperleukocytosis in AIHA caused by Mycoplasma pneumoniae. Keywords: Autoimmune Hemolytic Anemia, Child, Leukocyte, Mycoplasma.