Though Italian maritime states were engaged in trade with Islamic Egypt and North Africa in the early middle ages, the crusades of the twelfth and thirteenth centuries greatly intensified commercial contacts between Muslims and Latin Christians in the eastern Mediterranean. The same Genoese, Pisan, and Venetian ships that transported pilgrims and crusader armies to the East also transported spices and commercial goods to the West. These intensified commercial relations between Italian maritime states and Islamic dynasties gave rise to new institutions and commercial practices to accommodate the increased volume of both goods and merchants in the ports of the eastern Mediterranean. Recent work on the development of the funduq/fondaco has greatly advanced our understanding of the spatial contexts of cross-cultural trade and the legal and social conventions that sustained and constrained trade between Muslims and Latin Christians in this period. However, if we know more than ever about how particular institutions (like the fondaco and the diwan) helped merchants negotiate the religious and cultural barriers to trade, we still know very little about how these merchants negotiated the ever-persistent language barrier between Muslim and Latin Christian merchants. How was language mediated in this moment of intensified trade between Islamdom and Christendom? Who was tasked to bridge the language barrier between Italian merchants and Muslim merchants and customs officials? In most studies of eastern Mediterranean trade in the crusader period, the problem of language and translation is rarely addressed. It is merely assumed that (nameless) translators must have been involved somehow. It is the aim of this paper to find out how by examining the roles of three officials affiliated with the diwan in this period—the katib, the tarjuman, and the simsar. Though they had different functions in the diwan, each official had a significant linguistic component to their job—whether drafting bilingual documents, ratifying sales between Italian and Muslim merchants, or acting as the middleman between foreign merchants and locals at the auction. Employing both Latin diplomatic treaties and Arabic fiscal treatises, I will reconstruct the translation practices and personnel of the Islamic diwan in the crusader period and reflect on the crucial—and often neglected—role of translators in facilitating the movement of goods and people in the medieval eastern Mediterranean.