Europe has a strong interest in and a history of assisting Iran in controlling inflows of drugs from Afghanistan. But due to Iran’s increasing use of the death penalty in drug trafficking cases, Europe has terminated its cooperation. Based on interviews with Iranian policy-makers and representatives of both human rights organizations and the United Nations Office on Drugs and Crime (UNODC), this article presents Denmark’s withdrawal of drug control funding in 2013 as a case study, analyzing the dilemmas and trajectories of joint Iranian-European drug diplomacy and the prospects for reengagement following the nuclear agreement.