The US response to the 1978-79 Iranian Revolution has been much written about yet remains shrouded in ambiguities and misconceptions. Drawing on recently declassified US government documents, this paper reframes our understanding of the US response to the revolution by exploring how a pervasive anxiety about the Iranian left and the Soviet Union drove US policy from 1978 through the early 1980s. Studies of the Carter administration’s reaction to the Iranian revolution have relied on journalistic accounts and the memoirs of US and Iranian officials, which are problematically influenced by their political agendas. The historiography has also been colored by 40 years of US-Iranian antagonism. Records of the secret deliberations of the Carter administration provide an opportunity for reassessment, revealing that the anti-communism of US officials and their fear of leftist revolution trumped their concerns about Ayatollah Ruhollah Khomeini. As unrest swelled in Iran in 1978, US officials looked with paranoia for the hand of the Soviet Union. Once the Shah fled in January 1979, the Carter administration saw Khomeini as a tolerable element within the new government and initially sought an accommodation to counter the left and the Soviets. Khomeini shrewdly played into American anti-communism, communicating through secret channels that he shared this orientation. While the Iran hostage crisis darkened the Carter administration’s views of Khomeini, US officials continued to worry that a Khomeinist collapse would empower the Iranian left, and as a result directed US covert action programs in Iran to focus principally on weakening the left and countering the Soviets. US officials ultimately doubted that Khomeini could form an enduring government, believing that as an elderly cleric, he was a short-lived figurehead. These views revealed the policy consequences of deep American cultural and religious prejudices, which saw Islam as inherently conservative and incapable of sustaining mass revolutionary politics. The paper also modifies our understanding of the struggle between Khomeinism and the Iranian left over the fate of the revolution, showing the tacit and sometimes direct aid that the US provided for the Khomeinists. The relationship between the US government and the Islamic Republic of Iran was, in short, not an inevitable animosity from the beginning. Initially, the two governments kept open the door to cooperation on the basis of their shared anti-leftism: an inconvenient history for both governments today.