Communities based on Sargassaceae have various ecosystem functions. However, the resource status of Sargassaceae beds in subtropical seas and their value as conservation targets remain unclear. The purpose of this study was to evaluate changes in the distribution of Sargassaceae species and the commercial value of Sargassaceae, and to determine whether there are gaps in knowledge about the distribution, use, management, and conservation of Sargassaceae species on Okinawa Island. For this purpose, we examined the occurrence records of Sargassaceae to determine the distributional changes from the past and inferred future changes of Sargassaceae bed using future water temperature projection datasets. In addition, through a literature review and interviews, we clarified how Sargassaceae is used, managed, and conserved in the island. Comparing the records of occurrence prior to 2000 with those of recent years, it is clear that the number of sites where occurrence was confirmed on the west coast of the island has decreased significantly. Sargassaceae is recognized for its role as a sea vegetable and nursery for sea urchins but monitoring and conservation activities of the Sargassaceae community are very limited. In addition, there are several points that were not in accordance with the actual situation, such as the listing of widely distributed species in the Red List. Based on the literature data, the tolerance of Sargassaceae species to high water temperature in Okinawa Island was summarized, and it was suggested that a monthly-mean water temperature increase of about 2 °C compared to the current level would not have a significant impact on their growth. Although it is assumed that Sargassaceae beds will be maintained, present monitoring and conservation systems are not sufficient. Therefore, it is important to strengthen the management system and to properly recognize and utilize the value of the Sargassaceae community sustainably.