This article identifies the key factors either supporting or blocking the implementation of the Right to the City concept in the urban planning systems of Brazil and Poland. Poland and Brazil, despite some differences, can be compared from the perspective of selected features of spatial planning systems. A characterisation of the spatial planning systems of both countries, including their legal and socio-political conditions, is made. The article identifies these institutional challenges and barriers in both national spatial planning systems, which can be linked to a discussion of the Right to the City concept. It then analyses how elements of the Right to the City concept are implemented in each system and what constitutes the main barrier. Those elements of the Right to the City concept that can be more universally compared were identified. The commonalities and discrepancies found in the two systems are then discussed. In Brazil, the Right to the City concept is much more strongly framed in formal and legal terms, but market and social inequalities are a barrier to its implementation. In Poland, on the other hand, there is a broader institutional inertia in the implementation of the concept. In both countries, there are serious (different) barriers related to the implementation of the Right to the City concept in the urban planning system.