Kearney's bluestar (Amsonia keameyana) is a highly endangered herbaceous perennial in the family Apocynaceae. The species is found only in the Baboquivari Mountains of southern Arizona. We report the isolation and development of 12 microsatellite loci for Kearney's bluestar. Numbers of alleles ranged from two to four and observed heterozygosities ranged from 0.20 to 0.80 in the nine loci found to be polymorphic in the test population. All loci were also tested for cross-amplification in five other Amsonia species representing two sub-genera from the southwestern United States. Some loci that were not polymorphic in the Kearney's bluestar were polymorphic in other species.