Cassava, Manihot esculenta Crantz (Euphorbiaceae), is a major tropical crop. It is a diploid and sexually fertile, but confined to vegetative propagation in agriculture. While polyploidization is a major evolutionary process in higher plants and is of importance in the creation of improved crop varieties, spontaneous polyploidization is poorly documented for M. esculenta. Molecular and cytological evidence is provided here for two cases of intraspecific triploidization events that occurred in smallholders' fields in Vanuatu, South Pacific. We then discuss the implications of triploidy for the crop and highlight the importance of this discovery for the evolution of this species in traditional cropping systems.