Elderly patients with acute myeloid leukemia (AML) have been found to clinically benefit from the combination of azacitidine (AZA) and venetoclax (VEN), although the safety and efficacy of the treatment in extremely elderly patients (age >85 years) have not been fully established. An 88-year-old woman diagnosed with AML was given a lower dose of AZA and VEN. She eventually developed grade 4 hypokalemia, necessitating treatment interruption. However, a lower dose of VEN was successfully continued in the subsequent cycle of treatment, resulting in complete remission. Hence, reduced AZA and VEN doses may be beneficial for extremely elderly AML patients.