Although informal groups of member states often steer EU foreign policy, existing scholarly literature does not offer an overarching theoretical approach to account for their causes and their different types. This article conceptualizes informal groupings and offers a theoretical approach that explains their occurrence in EU foreign policy. It claims that while disagreements among member states and the lack of EU capacity are the main causes of informal groupings, the combination of these two factors over time and across different policy issues determines the emergence of specific types of informal groupings in EU foreign policy. Indeed, evidence from Kosovo, Libya and Syria shows that different types of informal groups addressed various policy issues by replacing, complementing and/or Manuscript -with author details supporting corresponding EU policies. Nonetheless, as these groupings lack central guidance and accountability mechanisms, they are not a panacea for EU foreign policy.