Mitochondrial cytochrome oxidase I and II genes were sequenced for two invasive alien birch (Betula L. [Betulaceae]) leaf-mining sawflies, Profenusa thomsoni (Konow, 1886) (Hymenoptera: Tenthredinidae) and Scolioneura betuleti (Klug, 1816) (Hymenoptera: Tenthredinidae), accidentally introduced from Europe to North America. Ten North American and two European populations of P. thomsoni were sampled. As no genetic variation was observed for this parthenogenic species in Europe or North America, there is no evidence that this species was introduced more than once into North America. A single Canadian population of putative S. betuleti was genetically characterized and compared with populations of S. betuleti and Scolioneura vicina Konow, 1894 in Europe to resolve the species identity of the introduced Canadian population. Three haplotypes were present in European material but only one haplotype was represented in material collected in Canada. The haplotype in the Canadian population occurred in both S. betuleti and S. vicina in Europe. Thus, this preliminary genetic work cannot provide certain identity of the Canadian species. Moreover, there was no significant genetic difference between putative S. betuleti and S. vicina in Europe, leading us to suggest that S. vicina may not be reproductively isolated from S. betuleti, despite ecological differences.