We characterized variation within the mitochondrial genomes of the invasive silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) from the Mississippi River drainage by mapping our Next-Generation sequences to their publicly available genomes. Variant detection resulted in 338 single-nucleotide polymorphisms for H. molitrix and 39 for H. nobilis. The much greater genetic variation in H. molitrix mitochondria relative to H. nobilis may be indicative of a greater North American female effective population size of the former. When variation was quantified by gene, many tRNA loci appear to have little or no variability based on our results whereas protein-coding regions were more frequently polymorphic. These results provide biologists with additional regions of DNA to be used as markers to study the invasion dynamics of these species.