This is a case of visceral larva migrans and hypereosinophilia syndrome with persistently elevated white blood cell count despite adequate medical therapy in a 4-year-old boy with leukocytosis and splenomegaly. Medical history included reactive airway disease and geophagia (pica). Serology for Toxocara canis revealed elevated IgG and IgM titers. Ophthalmologic evaluation ruled out ocular larva migrans. After 5 days of thiabendazole therapy, leukocytosis persisted, and a second course of anthelmintics was prescribed. Two weeks later, a decrease in leukocytosis was noted. Thiabendazole therapy was continued for 15 more days. Repeated serology for T canis revealed a decreased IgM titer and a further elevated IgG titer. Follow-up showed increased physical activity, improved respiratory status, and resolution of splenomegaly.