Loss-of-function mutations in telomerase complex genes reduce telomerase activity, and can clinically manifest as bone marrow failure disease, which predisposes to acute myeloid leukemia (AML). Telomerase dysfunction also leads to short telomeric overhang, which is a crucial telomeric structural component, and potentially results in chromosome instability. We screened variants in telomerase reverse transcriptase (TERT) and telomerase RNA component (TERC) genes, and investigated the 3'-overhang length in bone marrow samples from 72 Chinese patients with AML (61 de novo, 11 secondary, excluding M3), aged 13-77. Cytogenetics, disease severity and short-term survival were evaluated. Three TERT mutations (n896G>A, n1079C>G and n1451G>C) were identified. Mutation carriers had short overhangs and a poor prognosis. We found that overhang lengths were much shorter in AML compared to normal controls (p < 0.001). Short overhangs were related to a high percentage of karyotype abnormalities and poor prognosis (73.8% in short overhang group vs. 30% in normal group, p=0.001). Multivariant analysis showed that overhang length, age and unfavorable chromosome abnormalities served as independent prognostic markers in AML (Cox regression, p=0.001). These data raise the possibility that short overhang length may predict poor prognosis in patients with AML. These findings would have to be confirmed in large, prospective studies.