Annona vepretorum Mart. (Annonaceae), popularly known as ‘bruteira’, has nutritional and medicinal uses. This study investigated the chemical composition and antitumour potential of the essential oil of A. vepretorum leaf alone and complexed with b-cyclodextrin in a microencapsulation. The essential oil was obtained by hydrodistillation using a Clevenger-type apparatus and analysed using GC-MS and GC-FID. In vitro cytotoxicity of the essential oil and some of its major constituents in tumour cell lines from different histotypes was evaluated using the alamar blue assay. Furthermore, the in vivo efficacy of essential oil was demonstrated in mice inoculated with B16-F10 mouse melanoma. The essential oil included bicyclogermacrene (35.71%), spathulenol (18.89%), (E)-b-ocimene (12.46%), a-phellandrene (8.08%), o-cymene (6.24%), germacrene D (3.27%) and a-pinene (2.18%) as major constituents. The essential oil and spathulenol exhibited promising cytotoxicity. In vivo tumour growth was inhibited by the treatment with the essential oil (inhibition of 34.46%). Importantly, microencapsulation of the essential oil increased in vivo tumour growth inhibition (inhibition of 62.66%).