Nest usurpation is a strategy in which an individual or pair of one species takes over the nest of another species. This is the first documented occurrence of a Piping Plover (Charadrius melodus) pair usurping an Interior Least Tern (Sternula antillarum athalassos) nest. The Piping Plovers incubated the three Interior Least Tern eggs in the nest, and all three eggs hatched. The adult Piping Plovers accompanied and brooded the Interior Least Tern chicks for 1 day post-hatching, but we did not see the adult Piping Plovers nor the Interior Least Tern chicks after that day. The Piping Plovers likely usurped the Interior Least Tern nest because they developed hormonemediated broodiness after they lost the eggs from their two previous nesting attempts. When the Piping Plovers encountered an unattended Interior Least Tern nest with eggs, they instinctively took the nest and its contents as their own.