Blackfishes (Esociformes: Esocidae: Dallia), small fishes with relictual distributions, are unique in being the only primary freshwater fish genus endemic to Beringia. Although the number of species of Dallia is debated, disjunct populations and distinct mitochondrial divisions that predate the end of the last glacial maximum are apparent. We developed sixteen polymorphic microsatellites from the Alaska blackfish (Dallia pectoralis) to study genetic diversity in Dallia. Genotypes from two populations, Denali (n = 31) and Bethel (n = 35), demonstrated the usefulness of the loci for population-level investigation. Observed and expected heterozygosity averaged 18.6 and 19.8 % in Denali and 61.1 and 63.7 % in Bethel. Number of alleles at each locus averaged 3.50 in Denali and 9.63 in Bethel. The observed signature of variability and structuring between populations is consistent with mitochondrial data.