Many evaluations of terrorist disengagement have focused on the end of violent activity at the individual level. This chapter offers a definition for disengagement and some of the reasons that it occurs at the individual and organizational levels. It describes de-radicalization and discusses several of its drivers. Although the concepts of disengagement and de-radicalization are closely associated, confusion about their meaning and the degree to which they are used interchangeably demands their conceptual distinction. The chapter provides a brief synopsis of how these concepts differ and the implications of distinguishing them conceptually. It also provides references to guide the motivated reader to readings that expand upon these initiatives and other issues concerning disengagement and de-radicalization. Like disengagement from terrorism, there are multiple reasons why an individual may experience de-radicalization at any point in his/her involvement with a terrorist group.