Nest depredation is a major source of mortality in many turtle populations. Although turtle life histories may have evolved with relatively high levels of nest depredation, present-day levels may be negatively impacting populations that are already declining. This degree of depredation may be problematic for species such as Macrochelys temminckii (Alligator Snapping Turtle), which has relatively low reproductive output for a large turtle, yet little is known about depredation of M. temminckii nests. We constructed 90 artificial M. temminckii nests in 2008 and 2009 at Black Bayou Lake National Wildlife Refuge in Louisiana to identify nest predators and elucidate patterns of nest depredation. All artificial nests were depredated, with Procyon lotor (Raccoon), and Dasypus novemcinctus (Nine-banded Armadillo) being the two most common nest predators. Other predators included Lontra canadensis (Northern River Otter), Didelphis virginiana (Virginia Opossum), and Lynx rufus (Bobcat). Nest depredation is a major threat to Alligator Snapping Turtles at this site and may be limiting recruitment in this population.