Guatteria blepharophylla Mart. (synonym Guatteriopsis blepharophylla Mart.) and Guatteria hispida (R.E. Fr.) Erkens & Maas (synonym Guatteriopsis hispida R.E. Fr.) belong to the Annonaceae family and are found in the Brazilian and Colombian Amazon basin. Both species are popularly known as ‘envira’ or ‘envireira’. In the present study, the leaf essential oils of G. blepharophylla (EOGB) and G. hispida (EOGH) were selected to investigate their cytotoxic effects. Tumour cell lines were treated with increasing concentrations of both essential oils for 72 h and analysed by a methyl-[3H]thymidine incorporation assay. The pro-apoptotic effect of these essential oils was assessed in HepG2 cells by morphological analysis (using haematoxylin/eosin staining and acridine orange/ethidium bromide staining), flow cytometry (cell membrane integrity and internucleosomal DNA fragmentation analysis) and a caspase-3 activation assay after 24 h incubation. Both essential oils displayed potent cytotoxicity in different tumour cell lines. EOGB showed IC50 values from 6.03 to 16.46 µg/ml for HepG2 and K562 cell lines, and EOGH showed IC50 values from 5.45 to 24.89 µg/ml for HepG2 and K562 cell lines, respectively. Cell morphologies consistent with apoptosis and a remarkable activation of caspase-3 were observed in the HepG2 cells treated with essential oils for 24 h. Significant increases in internucleosomal DNA fragmentation without altered membrane integrity were also found. In conclusion, both essential oils investigated were able to inhibit tumour cell proliferation and induce cell death by apoptosis pathways. Copyright © 2014 John Wiley & Sons, Ltd.