Primary myelofibrosis in childhood is a rare occurrence. We report a case of 12-year-old female who had a three year history of progressive abdominal distension with two months history of increasing pallor and associated symptoms. On evaluation she was found to have primary myelofibrosis with a novel frameshift deletion in the Calreticulin gene leading to premature truncation of the protein. Patient responded to hydroxyurea and low dose steroid therapy. Our case highlights the typical adult like presentation with a novel mutation in CALR gene, emphasizing the need to perform mutational analysis in pediatric myelofibrosis with no secondary etiology