The Keyi Mappila Muslim merchants of Tellicherry (Thalassery) on the Malabar Coast were one of the few early modern Indian merchant groups who succeeded in carving out a powerful political and social configuration of their own on the western coast of the Indian Ocean during the British period. Today, several branches of Keyi families remain a cultural unit in the Islamic community of Kerala. This article attempts to locate the group in the larger theoretical context of Indian Ocean cosmopolitanism and argues that the Keyis developed a distinct and significant type of coastal cosmopolitanism in an Indian Ocean setting; Chovakkaran Moosa, an influential merchant from a Keyi family during the colonial period, serves as a representative figure. Through their trade and financial relationships with British and local elites, and the characteristic architecture of their warehouses, residences, and mosques, the Keyis successfully integrated the practices of a global cosmopolitan space into a local vernacular secluded commercial space. This article presents a synthesis of a lively coastal urban and local rural cosmopolitanism that included several networks and exchanges, foreign and native collaborations, and an amalgamation of local and external cultural spheres. © Koninklijke Brill NV, Leiden, The Netherlands.