Abstract. Prolonged coral reef damages due to natural and anthropogenic factors may lead to fish habitat changes. The habitat alteration will make the necessary study of fish community structures. This study was conducted in the 12 stations of the Weh Island reef waters. The purpose of this study is to provide baseline data for monitoring activities in the future. The study objective is to identify the reef fish community structures in terms of diversity, species composition, density, and biomass. Methods used was belt transect and visual census within transect areas of 350 m2. The results showed that there were at least 126 species of reef fishes with 18 families included in the fishing targeted group and the indicator fish group. Those respectively consisted of 23 corallivorous species, 36 herbivorous species, 53 carnivorous species and 14 zooplantivorous species. Their species number, density and biomass were varied among transect sites. The dominant species of corallivores were Hemitaurichthys zoster, Chaetodon guttatissimus, Chaetodon colare, Chaetodon trifasciatus, Forcipiger flavissimus, Chaetodon vagabundus, Chaetodon meyeri, Chaetodon kleinii, Heniochus singularis, and Heniochus pleurotaenia. The dominant species of herbivores were Acanthurus leucosternon, Ctenochaetus striatus, Acanthurus tristis, Ctenochaetus truncatus, Zebrasoma scopas, Chlorurus sordidus, Acanthurus triostegus, Scarus niger, Scarus ghobban and Acanthurus auranticavus. The dominant species of carnivores were Pempheris vanicolensis, Odonus niger, Mulloidichthys vanicolensis, Scolopsis ciliatus, Parupeneus barberinus, and Scolopsis bilineatus. The dominant spcies of zooplanktivores were Pterocaesio tile, Caesio xanthonotus, Sargocentron caudimaculatum, Myripristis berndti, Caesio caerulaurea, Pterocaesio randalli, Pterocaesio chrysozona, Caesio varilineatus andMyripristis kuntee. Species diversity of fish indicator and target fishes are relatively high. Among of the dozen study sites that have excellent conditions of diversity, ...