The security-development nexus describes the complex interlinked relationship between the peacebuilding arenas of security and development. Based on the understanding that re-establishing basic security and development conditions is indispensable to sustainable peace, dominant donor policy frameworks present security and development as inextricably linked: low levels of security and development reinforce each other in a vicious circle, while high levels are expected to influence each other positively. Consensus on this paradigm has called forth integrated approaches to peacebuilding that have dominated the liberal peacebuilding agenda during the past two decades. However, applying the nexus on the ground has resulted in considerable challenges ranging from the securitization of development to coordination problems between security and development actors, which contributed to the failure of a number of peacebuilding missions in recent years. This chapter follows the evolution of the security-development nexus over time and analyzes specific challenges it encountered when implemented. Based on the criticism launched against the nexus, the chapter ends with a discussion of the utility of the paradigm in future peacebuilding endeavors.