The  OEH is a separate office within the NSW Department of Premier and Cabinet. It is an environmental regulator and a manager of parks and gardens in NSW and develops and leads policy and reform in sustainability, biodiversity and native vegetation, coastal protection and Aboriginal cultural heritage.

OEH manages 6.8 million hectares of national parks and reserves, which is almost 9 per cent of NSW.

OEH was formerly known as the Department of Environment, Climate Change and Water (DECCW) and the DECCW annual reports provide a useful overview of previous work and achievements