The principle of the best interests of the child is regularly referred to by the European Court of Human Rights in its jurisprudence involving children. However, the principle is notoriously problematic, and nowhere more so than in the immigration context where the state's sovereign interests are keenly at stake. This article critically examines the expulsion and first-entry jurisprudence of the European Court of Human Rights under Article 8 of the European Convention on Human Rights, interrogating whether a 'principled' approach is adopted to the best interests principle. It is argued that a principled approach is one which sees the best interests principle interpreted in the light of its parent document, the UN Convention on the Rights of the Child, as interpreted by the UN Committee on the Rights of the Child. It is demonstrated that despite widespread recourse to the best interests principle, the European Court of Human Rights fails to adopt a rights-based approach when identifying the best interests of the child and does not always give sufficient weight to the best interests of the child when balancing the interests of the state against those of the individual. The analysis also reveals a way for the Court to develop a more principled approach to the best interests principle.