This dataset contains sampling information and genetic data of 12 novel microsatellite loci developed and polymorphic in the Sea Sandwort (Honckenya peploides) and screened in Merckia (Wilhelmsia physodes) from Alaska. The allele sizes for the 12 microsatellite loci developed in this study are included for two populations of Sea Sandwort (Fossil Beach, Kodiak and Egg Bay, Atka) and one population of Merckia (upper Coleen River, Brooks Range).