Granulocytic sarcoma (GS), an extramedullary myeloid tumor composed of immature cells of the granulocytic series, can occur in patients with acute myeloid leukemia (AML), myelodysplastic syndrome, or chronic myelogenous leukemia. It can occur in any organ or tissue, but the most common involved areas are the skin, bone/spine, and lymph nodes. However, its occurrence in the gastrointestinal tract is relatively rare, and is especially rare in the colon in adults. No case of GS involving the colon in children has ever been reported. We report here an extremely rare case of GS in the colon of a 10-year-old boy with AML presenting with hematochezia. Colonic GS was diagnosed by colonofiberscopic biopsy. His hematochezia responded rapidly to induction chemotherapy and the patient remained in complete remission after 3-month follow-up. In conclusion, hematochezia may be due to colonic involvement of GS, which should be considered in the differentials in addition to thrombocytopenia, as it is usually encountered in AML patients.