Four species of sea horses (Syngnathidae: Hippocampus) were found in Peninsular Malaysia during a survey conducted between April and August 2001. These were Hippocampus trimaculatus, H. spinosissimus, H. kuda and H. kelloggi. All four species were found in the Straits of Malacca; two species (H. trimaculatus and H. spinosissimus) in the east coast of Peninsular Malaysia in the South China Sea; and three species: H. trimaculatus, H. spinosissimus and H. kuda in the south coast, Straits of Johor. There were habitat and depth separations by species. Hippocampus trimaculatus, which was found throughout the coastal waters of the Peninsular, were reported to inhabit chiefly among gorgonians at approximately 20–40 m depth. The habitat and depth in H. spinosissimus were rather similar to that of H. trimaculatus; but the former species was less widespread in the west coast. Hippocampus kuda was confined to shallow water between 1 to 3 m, and was found in seaweeds and sea grass meadows in a few estuaries; whereas H. kelloggi inhabited gorgonians and sea whips in deep-water below 65 m. Mean standard lengths are given. No sexual size dimorphism was detected in any of the species.