Thirty-eight species of xanthoid crab are recorded for the first time from Dhofar Province, southern Oman. The geographical range of three species [Nanocassiope alcocki (Rathbun 1902), Actumnus digitalis (Rathbun 1907), and Macromedaeus crassimanus (A. Milne Edwards 1867)] is substantially extended. The pattern of xanthoid species diversity is discussed in relation to the effect of the seasonal monsoon-driven upwelling, and compared with that of other parts of the Western Indian Ocean.