The objective of this work is the comparative analysis of public administration reforms in Brazil and Spain during the last third of the twentieth century to the present. The main trends of modernization studied in this research are New Public Management, governance and e-administration. The methodology combines the historical analysis, the comparative method and the documentary and empirical collection of the data extracted from both administrations. Among the conclusions are similarities and singularities of each case. In both countries, modernization began as an adaptive response to social changes and reforms focused on the granting, privatization and outsourcing of contracts with private organizations as providers of public services. Among the differences are identified that in Brazil the reforms were concentrated in a very short period while in Spain they were gradual and in tune with the European Union.