Atypical teratoid-rhabdoid tumor (AT/RT) is a rare but one of the most aggressive embryonal tumors of the central nervous system (CNS), most often occurring in children under 3 years of age. AT/RT accounts for about 1–2% of all CNS neoplasms and has a very poor prognosis, high risk of secondary tumor development, recurrence and/or metastasis in patients in remission and limited therapeutic potential. The clinical manifestations are usually symptoms of increased intracranial pressure. The mainstay of tumor treatment is complex chemotherapy combined with radiation therapy. A clinical case of sequential occurrence of two cancers (AT/RT and leukemia) in a 3-year-old girl is presented. © 2024 by the authors. Licensee MDPI, Basel, Switzerland.