How can a terrorist be trusting, trusted or trustworthy? The majority of us, understandably, could not fathom any situation where the notion of trust could be applied to terrorist actors. We envisage those who we trust as people of noble or decent character. However, it is posited here that trust has a significant part to play in our understanding of the psychology of terrorism, as well as the concept of terrorist violence in general. As the issue of trust is rarely analysed in relation to terrorism the purpose of this chapter is to propose a series of areas where it is believed that the application of a trust-based analysis can bring us closer to gaining a more holistic appreciation of involvement in a terrorist group. By building on this concept of trust with respect to terrorist involvement the chapter concludes by assessing the vital role that trust can play in countering terrorism, helping victims and drawing actors away from involvement in terrorist organisations.