This chapter focuses on the challenges of ensuring the accountability of peacekeepers in peacekeeping missions. Accountability for criminal misconduct involving corruption and resource exploitation is briefly discussed, but the main focus of the chapter is on sexual exploitation and abuse (SEA) by United Nations (UN) peacekeepers—one of the most widely documented areas in which lack of accountability for the transgressions of peacekeepers is most evident. The chapter includes a comprehensive and systematic survey, both empirical and theoretical, of the problem of sexual exploitation and abuse, as well as a discussion on the difficulties of policing peacekeepers. It concludes with suggestions and scenarios for transforming the current climate of impunity for peacekeepers into a culture of accountability and justice.