The marine environment of Southeast Asia is amongst the most ecologically important in the world. A substantial volume of international shipping passes through the region which can have a deleterious effect on the environment due to impacts including operational and accidental discharges, collisions and groundings. Recently Malaysia, Indonesia, Viet Nam and the Philippines have introduced or commenced work towards proposals for special measures to be adopted by the International Maritime Organization (IMO) targeting the risks of shipping. These proposed special measures are in the form of ‘particularly sensitive sea areas’ (PSSAs), and are being developed under a cooperation program between the IMO and the Norwegian aid organisation (Norad). This article analyses the PSSA proposals currently underway or recently finalised by Malaysia, Indonesia, Viet Nam and the Philippines, and the legal framework for the establishment and implementation of measures for environmental protection under the law of the sea and the IMO.