About 2500 Decapods and Stomatopods have been collected at Sar Uanle (Southern Somalia) by the Centro di Studio per la Faunistica ed Ecologia Tropicali of the Consiglio Nazionale delle Ricerche during the course of five expeditions conducted between 1971 and 1975. The material comes in part from the madreporic sublitoral platform, and the nearby rocky coast, and in part from the dune and the sandy beach. This paper deals with the decapods collected on the sandy beach, principal study area of the Centre, while the other material will be discussed separately.