Isospora belli, a coccidian parasite usually causes a self limiting illness of acute onset with fever, diarrhoea and colicky pain in a normal host. In immunocompromised patients human isosporiasis becomes chronic. We report a case of a malnourished 9 year old female child who presented with complaints of loose stools, nausea, vomiting and weight loss for the past three months. Stool examination revealed immature oocysts of Isospora belli. The patient was successfully treated with TMP-SMX.