The Yellow-breasted Crake (Porzana flaviventer) is a poorly-known Neotropical rail found in densely vegetated freshwater wetlands; a single nest record exists for Puerto Rico. In May 2001, the crake was detected in managed impoundments of the Humacao Nature Reserve, located in southeastern Puerto Rico. Yellow-breasted Crakes were regularly observed during monthly surveys of the impoundments with as many as nine individuals detected during an April 2002 survey. Systematic nest searches during 2001–2002 located fifteen nests in approximately 13 ha of newly created wetlands. The nests were more common in Eleocharis mutata, Cyperus ligularis, and Paspalum vaginatum. Nests had an average clutch size of 3.7 (±0.31) eggs and brood size of 2.7 (±0.5) chicks; hatching success was 65% and nesting success 40%. Six nests were depredated. The nesting activity of Yellow-breasted Crake at the Humacao Nature Reserve suggests wetland management in abandoned sugarcane areas of coastal Puerto Rico may benefit waterbird species of concern. Future research should determine abundance estimates and habitat relationships for this secretive species.