An anti-collision warning system for marine vehicle includes, an optical sensor covering at least partially the horizon of the marine vehicle, image processing means for extracting in real time from each image position information of objects visible on the surface of the sea, and anti-collision analysis means, which periodically calculate the evolution of the position information of each visible object, and which assess a risk of the marine vehicle colliding with each visible object according to the evolution of the position information of the visible object.