The principle of the best interest of the child has become as a red thread in the context of justice and, above all, in the context of decision-making. Aware of this, this paper analyzes how the principle in question is applied in the cases aimed at expulsion. It has been shown that foreign nationals and/or stateless persons may be deported. In this sense, minors and/or the parents of minors could also be expelled. In both situations, compliance with the principle of the best interests of the child is unavoidable. In order to see how this principle is applied, national jurisprudence was appealed to, as well as the European Court of Human Rights.