Abstract: This data set contains measurements of carbon (δ13C) and nitrogen (δ15N) stable isotope values of feather, skin, bone, and toenail samples of mummified Adélie penguin chick remains excavated from multiple sites around the Ross Sea region of Antarctica between 2004 and 2016, as well as the same measurements for modern Adélie chicks collected from the surface of Cape Hallett and Adelie Cove in January 2016. Stable isotope analyses were conducted using an elemental analyzer coupled to a continuous flow stable isotope ratio mass spectrometer. Where possible, accelerator Mass Spectrometry (AMS) radiocarbon dates on selected mummy tissues were completed at the Rafter Radiocarbon Laboratory, New Zealand (NZA), Beta Analytic, Inc. (Beta), the University of Georgia Center for Applied Isotope Studies (UGAMS), and Woods Hole National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) facility. All dates were corrected for the marine carbon reservoir effect and calibrated to calendar years before present (cal years BP) using a ΔR of 750 ± 50 years and the MARINE13 calibration curve in Calib 7.0 (2σ range). The data set also includes excavation/collection site names and latitude/longitude, date of excavation/collection, tissue used for radiocarbon dating, and carbon to nitrogen ratios. Details of the data set and all relevant methods are provided in Kristan et. al., 2019.