The Barack Obama administrations policy of engagement with Iran has been undone by the Donald Trump government. Various factors influenced both strategies including internal and external enablers and constraints that are part of any foreign policy making process. Trump first decertified the Iran deal and then withdrew from it and reimposed sanctions. The first section of this paper details Obama’s diplomacy towards Iran in an effort to better understand Trump’s actions. The second part looks at the parameters of the deal while the third addresses Trump’s response to it during his presidential campaign. Lastly, the paper examines the internal and external dynamics related to Trump’s policy towards Iran.