Abstract Mixed‐phenotype acute leukemia (MPAL) with FLT3‐TKD mutations is a rare and challenging subtype of leukemia. Effective management strategies are crucial for improving patient outcomes. A 31‐year‐old man with FLT3‐TKD‐mutated MPAL achieved hematological remission through the JALSG ALL202‐O protocol and gilteritinib, followed by cord blood transplantation (CBT). Post‐transplant complications included adenovirus‐induced hemorrhagic cystitis, managed with bladder irrigation and ribavirin, and engraftment failure, necessitating a second CBT on Day 35. Subsequent adenoviral conjunctivitis resolved with vidarabine. The patient achieved neutrophil engraftment by Day 76 and was discharged on Day 173 without relapse. This case highlights the importance of vigilant supportive care and tailored therapy in managing MPAL with FLT3 mutations, especially in the context of post‐transplant complications.
