Acute myeloid leukemia (AML) has been rarely reported after transplantation, namely seven cases described so far. The putative mechanism of action is long-standing immunosuppression, even though no clear correlation with the type of drug has ever been demonstrated. We report the case of a 28-year-old male patient who presented with a early onset of AML after liver transplantation for hepatitis B virus-related acute liver failure. The AML was characterized by aggressive clinical features with extrahematologic sites of involvement and an atypical immunophenotype; the laboratory findings were consistent with the diagnosis of monocytic acute leukemia.