Reintroduction is an effective tool for restoring endangered populations. There is increasing concern, however, that demographic restoration may not equate with genetic restoration. We examine the demographic-genetic contrast in the context of one of the world's most successful carnivore population restorations. Beginning in 1982, a total of 835 river otters Lontra canadensis were reintroduced to Missouri, USA, more than 50 years after extirpation. Most otters were translocated from Louisiana, USA, and released at 43 sites across the state. An estimated population of 11 000–18 000 otters existed by 2000, and density estimates for Missouri otters are now similar to those reported for populations across the continent, indicating demographic recovery. We used microsatellite genotyping and mitochondrial sequence analysis of DNA extracted from fecal samples from eight southern Missouri rivers, in conjunction with mitochondrial DNA (mtDNA) analyses from several native Louisiana otter populations, to evaluate the genetic diversity and population structure of otters within Missouri as compared with Louisiana. The Missouri population showed moderate to high heterozygosity and allelic diversity, similar to that of the source populations, but low mtDNA haplotype diversity. We detected five distinct genetic clusters distributed throughout the eight rivers, with no evidence of isolation by distance. These data collectively suggest that 30 years after restoration efforts commenced, Missouri river otters have retained genetic diversity levels similar to those of the source populations, but that genetic structure has not reached an equilibrium between migration and genetic drift. Thus, the Missouri otter population has made a robust recovery despite retaining the genetic signature of the reintroduction.