Family reunification is one of the fundamental elements of international and national policies concerning the protection of immigrants' and refugees' rights. Traditionally considered a way of legally gaining access to states, it continues to be one of the main driving causes for migration, also within Europe. Collecting interdisciplinary researches, the authors of this study provide an in-depth analysis of the current legal framework relating to family reunification. The first section is dedicated to a critical analysis of international legal standards concerning family reunification. In this context, the investigation was conducted through a multi-level approach, mainly taking into account the law and the practice of the United Nations Organization, the Council of Europe and the European Union. The second section focuses on national legislations, policies and practices of the EU Member States (Austria, Germany, Hungary and Italy) that are at the center of attention because of their involvement in migration.