Following an explosion at the Deepwater Horizon drilling rig on April 20, 2010, MC252 an estimated 3.19 million barrels of oil leaked into the Northern Gulf of Mexico over 87 days. The endangered Kemp's ridley sea turtle (Lepidochelys kempii [Lk]) has a long established record of using the area near the well as primary foraging grounds. Resulting short- and long-term negative impacts of the oil spill on sea turtles could induce changes in the health and fitness of the Lk population. MC252 oil is known to have entered the foraging areas. Consequently, stable carbon and nitrogen isotope signatures from MC252 oil should be reflected in the food web and in the tissues of organisms such as sea turtles. We measured carbon and nitrogen isosope ratios of satellite-tagged turtles to 1) assess changes in foraging strategies of nesting Lk sampled in 2010 (the year of the spill) and two subsequent post-spill years; and 2) estimate the proportion of females that were within the area affected by the oil spill, the latter via discriminant analysis. Scute samples were collected using a biopsy punch from turtles nesting at a long-term study site on the Lower Texas Coast (Padre Island National Seashore) and on the Upper Texas Coast (Galveston Island to Surfside Beach). Turtles included in this study were sampled only once. δ13C values in samples obtained from turtles nesting in 2011 and 2012 were significantly depleted (F3,96=4.76, p=0.004 ) compared to 2010 samples. In contrast, there were no significant differences in δ15N among years. The depleted carbon values correlate with the depleted carbon values of MC252 oil. The distinctive isotope values of the satellite tagged females provided data with which to identify turtles that were inside the oiled area