DNMT3B encodes a DNA methyltransferase implicated in aberrant epigenetic changes contributing to leukemogenesis. We tested whether DNMT3B expression, measured by NanoString nCounter assay, associates with outcome, gene- and microRNA-expression and DNA methylation profiles in 210 older (⩾60 years) adults with primary, cytogenetically normal AML (CN-AML). Patients were dichotomized into high versus low expressers using median cut. Outcomes were assessed in the context of known CN-AML prognosticators. Gene- and microRNA-expression, and DNA methylation profiles were analyzed using microarrays and MethylCap-sequencing, respectively. High DNMT3B expressers had fewer complete remissions (CR; P=0.002) and shorter disease-free (DFS; P=0.02) and overall (OS; P<0.001) survival. In multivariable analyses, high DNMT3B expression remained an independent predictor of lower CR rates (P=0.04) and shorter DFS (P=0.04) and OS (P=0.001). High DNMT3B expression associated with a gene-expression profile comprising 363 genes involved in differentiation, proliferation and survival pathways, but with only 4 differentially expressed microRNAs (miR-133b, miR-148a, miR-122, miR-409-3p) and no differential DNA methylation regions. We conclude that high DNMT3B expression independently associates with adverse outcome in older CN-AML patients. Gene-expression analyses suggest that DNMT3B is involved in the modulation of several genes, although the regulatory mechanisms remain to be investigated to devise therapeutic approaches specific for thesepatients.Leukemia accepted article preview online, 10 September 2014. doi:10.1038/leu.2014.267.