This chapter addresses relational radicalisation by examining the conditions under which there is an extremisation of intergroup attitudes among members of the majority society and Muslims. Specifically, the chapter analyses when members of the mainstream society express Islamophobia and when the members of immigrant-origin Muslim communities join radical movements. On the one hand, recent work draws attention to the need to further study Islamophobia in order to distinguish between a dimension of prejudice that corresponds to a negative attitude towards Muslims and a dimension of principles, value-based reasons that are more nuanced. For example, members of the majority society who disagree with the religious practices of Muslims may express this view either because they are prejudiced against that community or because they are committed to a form of secularism that prohibits religious practices for all other groups, including Christians. There is also the possibility that members of mainstream society claim to be committed to the principle of secularism, but in reality, they apply it only to Muslims. On the other hand, immigrant-origin Muslims may react differently to perceived rejection by the majority society. Faced with discrimination, they may respond with a withdrawal from national identity, a reinforcement of their identification as Muslims, and hostile attitudes toward the majority society. However, often, Muslims may claim membership in the national group. Recent research shows that when young Muslims experience a misrecognition of their national identity, they respond with an increase in their identification with the majority society. Extreme attitudes do not appear automatically; other conditions must be met in order to join radical movements, such as exposure to discourses that legitimise violence and insertion into a social network capable of implementing radical actions. Thus, a closer examination of the conditions under which Islamophobia versus radicalisation can manifest itself can allow for a better understanding of this relational radicalisation and facilitate the implementation of more targeted intervention programs.