The mangrove area in Mentawir Village has the potential to be developed into an ecotourism site in Nusantara Capital City (Ibu Kota Nusantara or "IKN"), Indonesia. Apart from the mangrove conservation area, some myths add to the tourist attraction of IKN. Various myths continue to live and develop in the lives of the Paser indigenous people in Mentawir Village (Sepaku District, East Kalimantan Province, Indonesia). The functionalization of the myth is expected to support mangrove ecotourism. So, how can existing myths affect the use of mangroves to support the development of mangrove ecotourism in IKN? Ethnographic data collection conducted through participatory observation and in-depth interviews can reveal the existence of myths that affect the use of mangroves in people's lives. The results showed that three myths developed in Mentawir Village: the myth of yellow mangroves (lemit mangroves/bakau lemit), the myth of the Mentawir River (Sungai Mentawir), and the mystery myth of the peace stone (misteri batu perdamaian). Using the Malinowski cultural functionalization approach, it can be seen that these myths can support the development of mangrove-based ecotourism and creative economy as IKN tourist attractions that can support community welfare.