In the Indian Ocean, the Comoros archipelago became independent in 1975 and the island of Mayotte remained part of France in 1979 before acquiring the status of French department in 2011. While the circulation between the four islands has been very important in the history of the Comoros, these changes have introduced and reinforced the control of maritime borders by the French state. In recent years, these political borders have been combined with the construction of social boundaries opposed to Comorian immigration, gradually built into a public problem, considered responsible for the difficulties of economic and social development of the island. The religious space has been kept away from these logics until recently and seems increasingly marked by the ethnicisation of social relations. Based on a postdoctoral research conducted in 2018, this article analyses the structure of the Muslim cult in Mayotte, which values the religious knowledge acquired outside the island, while promoting the legitimacy of their local anchoring. Consequently, two logics combine (autochthonisation and othering) and place the Mahoran and the Comorian believers in an unequal position in the mosques, and especially in the access to the imamah.