The content of this chapter describes the processes by which individuals become radicalized toward militant jihadi terrorism and ultimately join terrorist groups using ISIS recruitment and radicalization within ISIS as the focus of doing so. In doing so, it identifies steps that practitioners and policy makers can use to prevent and counter violent jihadist extremism by taking a nuanced approach that considers psychosocial vulnerabilities and environmental factors that contribute to radicalization. The case studies presented to illustrate these points are gleaned from the 240 interviews  with ISIS defectors, returnees, and imprisoned cadres interviewed by the first author, a research psychologist, in her role as director of the International Center for the Study of Violent Extremism (ICSVE) and well as hundreds of terrorists from other groups. In the case of the ISIS interviews, with the interviewees’ consent, the interviews were video-recorded and cut to create short counter narrative clips that can be used as a powerful tool for challenging the beliefs that individuals who have been exposed to ISIS propaganda may hold. This chapter also focuses on the Internet campaigns that ICSVE has used to test various aspects of the counter narrative videos, revealing the best ways to utilize the counter narratives and to maximize their impact online. Given that ISIS has become notorious for its skill at Internet recruitment and creating high-quality propaganda videos, it is imperative that counter terrorism professionals are able to parallel their efforts in order to continue fighting them even after the territorial defeat of the Caliphate.