This chapter focuses on developing a better understanding about online violent youth radicalisation in the context of prevention through restorative justice and positive psychology. The chapter is based on a case study that was carried out between December 2020 and December 2022, and involved pilots in the UK, Cyprus, Greece, Belgium, and France. Emphasis was given on the impact of COVID-19, including the lockdowns and the subsequent increase of youth online activity. The chapter is divided into four sections. The first provides a short account of the case study, its objectives, and adopted research methodology. The other two sections reflect the project’s two scientific blocks. The first block aimed at understanding the status quo of online violent youth radicalisation in the five project countries. The second used the data from the review to carry out fieldwork in the five project locations to triangulate the desk-based findings. The final section critically summarises the lessons from the project, leading to the construction of a curriculum that draws from the RJiNEAR principles, and focuses on preventing online violent youth radicalisation through positive psychology and restorative justice. Key lessons are drawn from the case study including the increasingly growing dimension of virtual paths to building behaviours that lead to violent extremist views, and the decrease in agencies’ preparedness for prevention and control.