This paper analyses Article 208(1) TFEU, which establishes what is commonly called 'policy coherence for development' as both an objective and an obligation for the EU's development cooperation policy. It argues that, as an obligation, Article 208(1) TFEU requires the EU – meaning each institution – to take into account development objectives in the formulation and implementation of any policy likely to affect developing countries. Should it fail to do so, any measure adopted by the EU is liable to annulment. In addition, the EU can be required to act if its omission violates a duty to act under Article 208(1). On the other hand, Article 208(1) TFEU does not contain an obligation of result. So long as the relevant EU institution has duly considered development objectives, it will have discharged its duty. The paper also discusses the ways in which the EU institutions can meet this obligation, including conducting impact assessments. It argues that, seen in light of the principle of proportionality, EU measures that are not based on a process that has taken into account development objectives are vulnerable to annulment. Finally, it discusses the enforcement of Article 208(1) TFEU: in other words, what can be done if the EU fails to take development objectives into account in its decision-making, especially in connection with the EU's substantive external human rights obligations under Article 21(3) TEU.