Christianity and colonialism are often closely associated because Christianity is the religion of colonial Europe and acted as its arm in Asia and Africa. Although colonialism is a form of imperialism and both, in the imperial belief, are meant to bring liberation to human rights to suppressed people, the 20th century historians argue that the role played by missionaries is quite arguable. Some modern historians portray missionaries as arrogant agents for colonial powers, and some look at them as visible agents for change or as saints and humanitarian people who introduce change into the lives of people whom they encountered, if only because their relatively selfless interest in the region compared so favorably with the colonialism of the European powers. As far as Arabia and the Gulf is concerned, they came into contact with American mission activates from the late 19th century.The American presence was clear in the presence of Protestant missionaries. Starting from the early 1890s, Protestant missionaries had begun journeying from New England to the Holy Land and the land of Arabia with the aim of converting Muslims. Although failed almost entirely to win Muslim souls for Christ, and many suffered terribly and lost their lives, they were successful in generating change in the whole region. Their success in leaving a lasting impression in the region in the form of educational institutions and hospitals are remarkable. These activities earned them quite goodwill among local people and many still regard them as agents of change. This reputation for disinterested benevolence was reinforced by the fact that many missionaries had shown some affection for the culture of Arabia as shown in their reports and writings. In addition, almost all of them adopted either Arabic names or Arab culture as a mean to be acceptable form the local. The aim of this paper is to shed a light on the activities of American missionaries in the Arab Gulf in the post –colonial era and discuss the different aspects of mission work in the region. Although humanitarian and educational works were the most successful tool of American mission work in Arabia, other aspects of mission work were also vital for America . Issues such as US Government support for Missionaries and the way they viewed them as necessary tool to intervene in the region at a time when oil concessions where being granted, will also be explored.