Despite the precautionary approach being only recently applied to the management of international fisheries, it has raised considerable controversy. There are concerns over the precise legal meaning of the precautionary approach. There are also worries that strict application of the approach will be used to shut down some international fisheries. Moreover, there is continuing debate about how precaution should be applied to the management of fisheries where there has always been, and probably always will be, sparse scientific knowledge. Much of the demand for a precautionary approach to international fisheries management has come from environmentalists, but there has been little analysis of their views. This article seeks to explore the precautionary approach to fisheries management from an environmental perspective. The first part of the article discusses the status of the precautionary approach at international law and, in particular, addresses the question whether the approach has become founded in customary international law. The second part of the article provides an environmental perspective of the precautionary approach and its application to international fisheries. This part covers issues such as the demand by environmentalists for science-based management procedures, the setting of stock levels, anticipatory reference points, ecological safeguards and participation in decision-making.