Terrorist deradicalisation is not a new idea for Spain. Spanish authorities used this strategy for mainstreaming the members of Euskadi Ta Askatasuna (ETA), an ethno-nationalist terrorist organisation that carried out a massive campaign of bombings, assassinations and kidnappings for more than forty years until the group’s dissolution in 2018. Though Spain experienced a growth of Islamist extremism since the 1990s, it was only in 2016 that the current Spanish deradicalisation program for Islamist extremists started. The current program though still evolving, faces many structural challenges that limit its success. This chapter gives an overview of the current deradicalisation program in Spain and its contexts, outcomes and challenges.