Acute colonic pseudo-obstruction is characterized by dilatation of the large bowel without mechanical obstruction. Although the first step of the treatment is conservative management, mechanical decompression should be performed when symptoms persist. Recently, the efficacy of pharmacologic treatment has been reported in adults, but no such data have yet been reported in children for treatment of acute colonic pseudo-obstruction resulting from chemotherapy. We report a 9-year-old boy with acute colonic pseudo-obstruction caused by chemotherapy for brain tumor who did not respond to initial supportive therapy, but who was successfully treated with neostigmine.