Charles Hamilton, an American oil executive who worked in the oil industry between 1912 and 1957, culminating in his role as the Vice President of Gulf Oil corporation, noted in his memoirs: “Many persons feel that American commercial interests might not have had the opportunity to participate in the development of the great oil fields of the Middle East had it not been for the splendid work of the Arabian mission.” As Hamilton’s statements revealed, the first Americans in the Gulf region were not American engineers searching for oil reserves or businessmen seeking to obtain drilling rights, but instead, a group of American missionaries from the Reformed Church of America (RCA) who had arrived in the area in 1889. Over the next twenty years, the RCA would go on to open dozens of missionary stations throughout the Arabian Gulf, including what is now Bahrain, Iraq, Kuwait, Oman and Saudi Arabia. Their primary strategy for converting local Arab Muslims to Protestant Christianity included obtaining the good will of locals medical missionary work throughout the Gulf, including the building of hospitals. American Protestant missionaries believed that the technological advancements represented by medicine were reflective of the larger superiority of Christian civilization over Islamic civilization. Although American missionaries managed to convert only a handful of Arab Muslims, their expansive and impressive network of connections throughout the Arabian Gulf, forged primarily through their medical work, reached the highest level of political power, including Ibn Saud himself. It was this very network that would not only set the stage for the discovery of oil in Saudi Arabia – but later facilitate the work of the engineers and businessmen who obtained American oil concessions with Ibn Saud. Although the missionaries’ local knowledge directly benefited American oil executives, it drew increasing suspicion from local British political agents, who saw the American missionaries as working hand in glove with Americans seeking to spread their commercial reach throughout Arabia, to the detriment of their own commercial and political power. This paper will analyze these tensions as British political agents sought to limit the rising influence of American missionaries in the Arabian Gulf in the first half of the twentieth century, the same decades that witnessed the slow erosion of British power in the Middle East.