Intraspecific diversity in Cassava Green Mite Mononychellus progresivus Doreste was examined using individuals collected in Benin and the Congo and in Columbia and Brazil. Comparisons were based on mitochondrial and ribosomal DNA sequences and the results of several cross-breeding experiments. Sequence variation was examined in a total of 1139 base pairs (bp) constituting the ITS2 ribosomal DNA (805 bp) and a fragment of the Cytochrome Oxidase I (COI) gene (334 bp). Sequence divergence is low, ranging from 0% to 2.1% for COI and from 0% to 0.4% for ITS2. Inter-strain comparisons have shown that the two African populations appear to be identical. They were similar to the Colombian population while the Brazilian population was clearly different. The data support the hypothesis of a single introduction of the species in the two African populations. Crossing experiments have shown partial hybrid sterility, suggesting a genetic incompatibility consistent with differences detected by sequence data. The results show the usefulness of molecular markers as a tool for determining taxonomic status and dispersion paths in spider mites.