Fiddler crabs play a significant role in the mangrove ecosystem in Poka Village, Ambon Bay. The fiddler crabs are crustaceans that are very important for the mangrove ecosystem in Poka Village, Ambon Bay. Anthropogenic activities are now causing damage to the mangrove environment of Poka Village. It is suspected that the oil spill from damage to the Poka PLTD pipe caused most of the mangrove vegetation to experience drought, which affected the survival of fiddler crabs (Uca spp.) living in the mangrove ecosystem habitat. The research was conducted between June and September 2023 in the mangrove environment of Poka Village, Ambon Bay. The purpose of this study was to analyze the morphological characteristics and distribution patterns of fiddler crabs (Uca spp.). Sampling was carried out at five observation stations using the purposive sampling method. Crab fiddle samples were identified based on morphological characteristics. The shape, color, and angle of the orbital shell and the morphology of the large claws of each type of fiddler crab (Uca spp.) are important characters in identification. The results of sample identification from five stations showed four species of fiddler crabs in the Poka Village mangrove ecosystem, namely Uca mjoebergi, Uca perplexa, Uca vocans, and Uca vomeris. In addition, this research found that each species of fiddler crab has a different spatial distribution; of the four species of fiddler crab found, Uca perplexa has a wide distribution on all substrates, while the distribution of Uca mjoebergi is limited to certain substrates.