Ocean noise, sometimes referred to as noise pollution, is the intentional or incidental introduction of human-generated (anthropogenic) sound energy into the marine environment. Examples of activities causing anthropogenic ocean noise include commercial shipping, recreational activities, natural resource exploration, underwater construction, scientific research and military sonar use. Whenever man interacts with the world's oceans, he puts sound energy into the water column. While considerable scientific uncertainty exists on the potential affects of anthropogenic ocean noise on the marine environment, some parties allege myriad adverse significant impact on living marine resources. The alleged impact runs the spectrum from reduced commercial fish catch rates to biologically significant behavioural impact, to marine mammal mass strandings, injury and mortality. In recent years, a number of scientists, environmental non-governmental organisations (NGOs), and international bodies have shown a growing interest in anthropogenic ocean noise and its potential adverse impact on the marine environment, especially living marine resources, such as marine mammals. This interest is the result of advances in acoustic and marine mammal behavioural sciences, aggressive strategic communication campaigns by environmental NGOs, and a series of highly publicised marine mammal mass stranding deaths allegedly linked to scientific research and military exercises. This movement has, in turn, led several international bodies, regional organisations, and international groups to address the issue, convene scientific inquiries, take policy actions and even call for domestic and international regulation of anthropogenic sound-producing activities. Assuming these groups successfully implement international or regional restrictions/prohibitions, what, if any, impact will be there to domestic and international maritime security? Are the relevant parties considering the impact as they propose, formulate and implement ocean noise environmental protection treaties, agreements and policies? Can environmental protection ever be a threat to maritime security? This article premises that regional or international regulation of ocean noise-producing activities, such as commercial shipping, natural resources exploitation and defence sonar use, constitute a non-traditional threat to domestic and international maritime security. It is a non-traditional threat precisely because most people think of activities purporting to advance environmental stewardship and protection of the world's marine resources as only beneficial endeavours. The anthropogenic ocean noise issue illustrates how some environmental protection actions can present unrecognised and often unaddressed, risks. Part One introduces the topic of anthropogenic ocean noise. Part Two summarises efforts by international and regional bodies to regulate anthropogenic ocean sound-producing activities through existing, modified and new international treaties, conventions and regional agreements. Finally, Part Three concludes that international regulations restricting or prohibiting vital domestic ocean sound-producing activities can result, if not safeguarded, in a significant threat to maritime security, national defence and the global economy.