Separated children seeking asylum in Europe have the right to a representative, typically in the form of a guardian, and the right to have their best interests taken into account. These rights are articulated in the Council Directives and Regulations regulating the Common European Asylum System. The original language used around the time of developing the Common European Asylum System related to ‘harmonisation’. This article, therefore, looks at the level of harmonisation of the systems of guardianship, and the guardians’ responsibility to determine and promote the best interest, for separated children seeking asylum in Europe. The article begins by defining the guardian and the best interest principle and outlining the relevant law, which presently exists in Europe. Three case studies were chosen to provide current examples of the differences in practice in Europe, namely: Belgium, Ireland and the Netherlands. The question dealt with in this article is to what extent the three case study countries meet the minimum standards set out in European law in respect of guardianship and the best interests of separated children seeking asylum.