Population change is increasingly being recognised as an important factor in shaping contemporary security challenges. States and non-state actors are concerned to find ways to govern population trends and dynamics in order to counter their effects on global security. The consequent expansion of the international security agenda to incorporate a wide range of population issues is considered from two angles in this paper. First, the paper examines how the securitisation of population affects the governance of demographic change: how has the construal of various population issues as security threats affected the ways in which they are governed? Second, the paper considers how recent population security debates may have reshaped our understanding of security and insecurity in international relations: is (in)security becoming re-defined as a demographic rather than a geopolitical problem, and what are the implications of this for the ways in which security is practiced?