Field surveys were carried out in 2002–2004 to assess the status, distribution and seasonality of waterbirds and coastal seabirds in Timor-Leste. A total of 3,653 records of 82 waterbird and coastal seabirds were collected during 446 visits to 74 wetland sites. Ten species new to Timor island were recorded: Green Pygmy-goose Nettapus pulchellus, Hardhead Aythya australis, Ruddy-breasted Crake Porzana fusca, Spotless Crake Porzana tabuensis (first Wallacean record since 1899), Common Coot Fulica atra, Greater Paintedsnipe Rostratula benghalensis, Spotted Redshank Tringa erythropus (second record for Wallacea), Pectoral Sandpiper Calidris melanotos (first record for Wallacea), Common Tern Sterna hirundo and Black-crowned Night Heron Nycticorax nycticorax. Significant populations of three Near Threatened species were recorded: Beach Thick-knee Esacus neglectus, Malaysian Plover Charadrius peronii and Darter Anhinga melanogaster. Three wetlands are highlighted for their importance: (1) Lake Iralalara (c.1,500 ha) is the most significant freshwater site in Timor-Leste and Nusa Tenggara, supporting at least 50 waterbird species including large populations of ducks and rails. It is an important staging site for Oriental Pratincole Glareola maldivarum (c.3,000 recorded in November 2004); (2) Tasitolu is a site of high national biodiversity significance with 53 waterbird and coastal seabird species recorded from its saline lakes and mudflats; (3) Kupang Bay in West Timor is the most significant site for migratory waders in Nusa Tenggara. Regular monitoring of key sites and further fieldwork are needed, especially along the south coast (Covalima, Manufahi and Manatuto districts).