The Islamic State of Iraq and Syria (ISIS) has been unprecedentedly effective in recruiting foreign terrorist fighters (FTFs). While Turkey has been a transit country and a major hub for ISIS’s logistical and human resources, it also has become a prolific hotbed for its recruitment. Based on face-to-face interviews and open-source reports, this paper provides an in-depth assessment of ISIS’s recruitment structure and the challenges that Turkey faces in relation to ISIS’s activities and FTFs. We conclude with a set of recommendations and a roadmap for pursuing effective and sustainable policies against ISIS. Overall, Turkey should adopt a paradigm shift on counterterrorism, transform the security and intelligence apparatus, and develop rehabilitation programs that consider the specificity of individuals’ radicalization at different levels.