Using an investigation into the un’s departments of Peacekeeping Operations and of Field Support, this article provides an overview of the environmentalization of peacekeeping operations. Growing environmental concern on the ground has resulted in bottom-up environmentalization, while top-down environmentalization can be seen in the un Secertariat’s environmental policy for all un field missions. Despite uneven implementation and limited greening, the Peacekeepers’ appropriation of the environment meets two strategic objectives : putting the environment on the agenda for security actors and bringing security and the environment into closer sync at the un.