BACKGROUND Anorectal infections occur in 5% to 9% of patients with hematological malignancies, including acute myeloid leukemia, and cause febrile neutropenia and sepsis. Surgical treatments of anorectal abscesses tend to be avoided in patients with leukemia owing to persistent neutropenia and bleeding risks. CASE REPORT A 56-year-old man presented with an ischiorectal abscess. Preoperative laboratory test results revealed leukocytopenia and anemia. He was diagnosed with acute myeloid leukemia. He developed septic shock. Antibiotic treatment was ineffective, and fever persisted. One week later, the abscess was treated by incision and drainage. Two days later, induction chemotherapy was initiated. No pus was drained; cellulitis spread to both buttocks. Pain worsened, and oxycodone was administered. Achievement of complete remission failed. Reinduction therapy was started, followed by fistulotomy of the abscess with extensive debridement of cellulitis on day 6. Granulation was observed on day 17. The patient's fever resolved on day 21. Although hematopoietic recovery was observed, bone marrow examination demonstrated partial remission. Two additional courses of chemotherapy were administered. Abscess recurrence was not observed, even during febrile neutropenia. The surgical wound shrank to a skin defect along the gluteal cleft. He achieved complete remission and was transferred to another hospital, where he underwent 3 allogeneic stem cell transplants. He died of leukemia progression. CONCLUSIONS Surgical treatments can prevent fatal progression of anorectal abscess, even during neutropenia. Incision and drainage are suitable for fluctuant abscesses. For a non-fluctuant abscess aggravated by sepsis and cellulitis, it is worth considering more invasive surgical interventions, including debridement and fistulotomy.