The authors propose that perceptions of injustice play a central role in radicalization toward violent extremism and terrorism. Perceptions of unfair disadvantage in comparison with other groups (horizontal deprivation) or by societal authorities (vertical deprivation) will elicit strong emotional and behavioral reactions. In combination with feelings of personal uncertainty and a lack of cognitive capacities to control justice-related emotions, this increases the pull and attraction of radical ideologies. Furthermore, when people join a radical organization, a vicious circle of identification with and justification of radical ideology and illegitimization and rejection of the status quo follow, possibly resulting in the justification of violence to achieve social change. Injustice perceptions are difficult to change, but a better understanding of the basic processes involved allows for the development of prevention and deradicalization programs, which should focus on full and just societal integration of groups and individuals that have a high potential to radicalize.