Community-based ecotourism (CBE) emerged to emphasize involvements of local communities for ecotourism sectors to realize effective equitable distributions of resources and profit from ecotourism, and self-development of people. However, success stories of CBE are reported as few. A CBE project “Iwahig Firefly Watching (IFW)” has been operated since 2008 by a local community. The main attraction is a firefly watching from a rowboat in a mangrove river. IFW has received international awards for the excellent operation. However, the ecological impact upon fireflies and the socio-economic influence of IFW have not been summarized yet. Hence, this study sought to reveal the characteristics of the fireflies and to summarize the IFW at the present. The ecology as it relates to fireflies (Coleoptera: Lampyridae) in the river was investigated. The importance of the existence of a variety of mangrove species for firefly display trees were found. Socio-economic study was also conducted to the involved locals of IFW, the non-involved locals and the tourists. Overall, their perspectives were positive upon IFW. Through this study, although some problems were raised, IFW was identified as a success case of CBE, which is rare in the world.