Recent developments have shown that the EU’s border security policy is greatly influenced by the US. This influence simultaneously has implications for other EU policies, including those on data protection. This paper highlights that policy-making at the transatlantic level is increasingly taking place through informal networks, such as the High-Level Political Dialogue on Border and Transportation Security and the High-Level Contact Group on data protection, which allow US involvement in EU policy-making. This tendency stems from the growing personal relationships among policy-makers, the gradual substitution of formal instruments with less formal contracts and informal understandings shaping the content of formal agreements. Drawing from empirical examples of EU–US cooperation on data protection in the context of homeland security, the paper analyses the repercussions of these developments and the issues that remain unresolved, and offers policy recommendations.