This work explores the interaction of American Protestant missionaries with Iranians during the 1960s and 1970s. It focuses on the missionary activities of four American Protestant groups: Presbyterians, Assemblies of God, International Missions, and Southern Baptists. It argues that American missionaries’ predisposition toward their own culture confused their message of the gospel and added to the negative perception of Christianity among Iranians. This bias was seen primarily in the American missionaries’ desire to modernize Iran through education and healthcare, and between the missionaries’ relationship with Iranian Christians. Iranian attitudes towards missionary involvement in these areas are investigated, as is the changing American missionary strategy from a traditional method where missionaries had the final say on most matters related to American and Iranian Christian interaction, to the beginnings of an indigenous system where a partnership developed between the missionary and the Iranian Christian.