The Wilson's Plover (Charadrius wilsonia) is widely distributed along the coast of the Americas. We present the first reproductive record in Baía de Todos os Santos, Brazil, broadening the southernmost limit of its breeding area along the Atlantic Coast to 12° 44′ S, 38° 45′ W. We recorded a family with a subadult in 2007, and a family with chicks and a nest in 2008. The female invested more time in incubation than the male in 96 hrs of diurnal nest observations. There were 102 interruptions during incubation due to the approximation of domestic animals (cattle and horses). The nest was abandoned 9 days after egg laying. An experiment with artificial nests suggests that 30% of Wilson's Plover nests may be destroyed by free-ranging domestic animals in this Baía.