We used nuclear and mitochondrial DNA (mtDNA, data archived in GenBank) markers to better understand historical population genetic structure and gene flow given relatively recent and ongoing reductions in sea ice habitats and changes in numbers of breeding adult Adelie penguins at regional rookeries along the western Antarctic Peninsula. Study nests near Anvers Island, where pairs of adults were present, were individually marked and chosen before the onset of egg-laying, and consistently monitored each season (2008-2009). When study nests were found at the one-egg stage, both adults were captured to obtain blood samples used for population genetic analyses. At the time of capture, each adult penguin was quickly blood sampled (~1 ml) from the brachial vein using a and non-heparinized, sterile 3 ml syringe infusion needle. After handling, individuals at study nests were further monitored to ensure the pair reached clutch completion, i.e., two eggs. Adélie penguin chicks at Avian Island were sampled over two years (2009-2010), Adelie chicks as Prospect Point were sampled during one year (2011), while chicks at Charcot Island were sampled during two seasons (2010-2011). Blood samples from crèched chicks (~1 ml) were taken from the brachial vein using a sterile 3 ml syringe and infusion needle following sampling procedures used for adult penguins. Genetic analyses were conducted at the wildlife genetics laboratory, Alaska Science Center - USGS, under the supervision of geneticist Dr. S.L. Talbot. Data presented here are raw data only and do not include any derived data products. For any meta-analyses with other microsatellite data, proper calibration across labs must be completed. Data were produced at the Alaska Science Center, USGS wildlife genetics laboratory under the supervision of Dr. Sandra Talbot (firstname.lastname@example.org). Questions regarding data or any laboratory cross-validation should be directed to Dr. Kristen Gorman (email@example.com).