Public diplomacy can be one element of multifaceted counter-terrorism strategy, but to be successful it must be used in timely fashion as a preventive tool. One key to reducing the threat posed by terrorism is to turn off terror groups’ recruiting faucets, and public diplomacy can play an important role in doing this. This article explores the vulnerability of certain populations and how they might be reached and strengthened in ways that undercut terrorist recruitment. This includes recognizing the importance of religion in terrorist recruiting and how it may be addressed constructively. Further, traditional pubic diplomacy programmes such as educational and cultural exchanges have been underestimated as a mean of counteracting the ‘othering’ that increases vulnerable populations’ susceptibility to terrorist recruitment.