Integration into the democratic system may induce the moderation of radical parties. This chapter assesses the extent of mainstreaming of populist radical right parties that follows their entry into local power. It does so through analysis of their discourse before and after attaining the leadership of the local government and considers four dimensions of mainstreaming. First, programmatic expansion and the relative salience of issues outside of their ideological core. Second, de-radicalization, in terms of the positioning towards and framing of the issue of immigration. Third, a softening of anti-establishment discourse and behaviour, considering both conflicts with other political actors and institutional reforms. And fourth, the self-presentation as normal and responsible, as opposed to a prior reputation for extremism and/or incompetence. To analyse changes across these dimensions, it draws from a range of data sources: council meetings, Facebook posts and newspaper articles. The chapter reveals cross-national differences in the extent of mainstreaming and suggests that institutional and party-strategic differences are crucial determinants of the extent and form of such change.