The Brazilian Constitution specifies substantive limits to amending power, however, it does not expressly authorizes the competence of judicial review of constitutional amendments. This fact was not an obstacle for the Supremo Tribunal Federal (STF) to assume such jurisdiction. In order to understand how the Supremo Tribunal Federal interpreted the unamendable clauses in the last 30 years, we developed an empirical research and collected all its decisions on the (un) constitutionality of constitutional amendments. There is an urgent importance on that issue since the new presidential government proposed a constitutional reform on pension rights, which, if approved, could be subject to judicial review in the STF. Based on a quantitative and qualitative survey, this paper demonstrates the level of judicial interference on the amending power in Brazil and indicates how the STF will protect the unamendable clauses if it follows its own precedent rulings in the next cases.