The reserve contains the 120-hectare (300-acre) Little Llangothlin Lagoon, part of the smaller Billy Bung Lagoon, and was established in 1979 under the NSW National Parks and Wildlife Act 1974. In 1996 the reserve was designated a wetland of international importance under the Ramsar Convention. It, with the adjacent area of Bagot Road, is also listed on Australia’s Register of the National Estate.
The Little Llangothlin Nature Reserve is an important site because it has some of the last high altitude freshwater lagoons on basalt soil on the New England Tableland. The reserve is situated in an area that has lost most of its vegetation to create arable land. It thus serves as a vital refuge for numerous species of birds, mammals, amphibians and reptiles.