This article discusses whether the EU–Turkey migration deal of 2016 is sustainable in the midst of divergent priorities and expectations of the parties, adverse results procured from the deal, and growing mutual distrust between the EU and Turkey. In so doing, first, it provides an overview on the background of Europe’s migration crisis of 2015–2016 and outlines the rationale behind and expectations from the deal. Secondly, the article critically reviews the performance of the deal to evaluate the extent to which it has met the expectations. It is explained that while Turkey has gained strategic leverage in its relations with the EU its government has to bear political costs at the home-front and shelve off its accession perspective. The EU, on the other hand, has managed to reduce the number of migrants using the Eastern Mediterranean route but has to endure constant threats of the Turkish government to withdraw from the deal and put up with its withering reputation as a normative power. Finally, by highlighting the expectation-outcome gap and the political cost the deal has induced to bear for both parties, this article demonstrates that the agreement has been circumstantial without a solid foundation, and any of the parties may opt-out once it regards the cost-benefit balance works unfavourably for them.