Central diabetes insipidus (CDI) is an uncommon complication of acute myeloid leukemia (AML). Patients present with polyuria either preceding or at the time of diagnosis of AML. We describe the case of a 36-year-old male who presented with a subacute onset of polyuria, polydipsia, nocturia, and fatigue. After an extensive workup, he was diagnosed with AML/CMML (chronic myelomonocytic leukemia) with a normal karyotype with DNMT3A, CBFB, and PTPN11 mutations. Further workup of the polyuria with a water deprivation test helped confirm the diagnosis of CDI along with MRI findings suggestive of hypophysitis. In this report, we analyze the clinical workup for AML and CDI and report the possibility of extramedullary leukemic infiltration associated with DNMT3A mutation, which has been reported as one of the mechanisms in the existing literature. We also discuss other theories hypothesized to cause CDI in AML patients with abnormal karyotypes. Our patient progressed to AML from CMML-2 after a cycle of decitabine, with confirmed gingival and presumed central nervous system (CNS) involvement. He is in minimal residual disease (MRD)-negative complete remission after induction with a CNS-active acute lymphoblastic leukemia-2 regimen. He also received double umbilical cord blood transplantation, conditioned with cyclophosphamide, fludarabine, thiotepa, and total body irradiation (TBI) of 4 Gy. This was complicated by engraftment syndrome for which he is currently being managed. CDI of the patient was corrected by desmopressin administration.