The embassy of Don García de Silva y Figueroa, sent in 1614 by Philip iii of Castile and ii of Portugal to negotiate an alliance with Shah Abbas against the Ottomans, was a fiasco. Not only did it fail to secure a deal, but within three years of the ambassador’s departure from Ispahan, in 1622, Persian troops, with the help of English ships, conquered the strategic island and fortress of Hormuz at the mouth of the Persian Gulf, marking a turning point in the decline of Portuguese power in Asia. For many historians the embassy was doomed from the start, notwithstanding the lavish gift offered to the Safavid ruler, because the Spanish ambassador could never offer Shah Abbas what he wanted. This analysis however assumes that the two sides understood each other perfectly well, and that the cultural distance between the ambassador and Shah Abbas was no obstacle to perfectly accurate political calculations. Taking advantage of the plurality of agendas and perspectives that can be documented during these exchanges, including English adventurers and commercial agents, various Carmelite and Augustinian friars, and the independent observer Pietro della Valle, this article seeks to test the degree of cultural commensurability in inter-cultural diplomacy, proposing a model that takes account of cultural distance without falling into a facile version of cultural relativism.