This study introduces the concept of multiple simultaneous peace operations (MSPOs). Two or more peace operations deployed at the same time in the same conflicts are MSPOs. There are numerous conflicts in which a United Nations peace operation works side by side with the peace operations of regional international organizations. The majority (60%) of all peace operations from 1978-2009 are MSPOs. Multiple simultaneous peace operations are also the 21st century’s trend for deployments. This study provides a description of a new dataset on multiple simultaneous peace operations and argues for analyzing peace operations through the lenses of MSPOs. Th is concept is useful for understanding inter-organizational cooperation in peace operations and the eff ectiveness of peace operations. It could also be used to apply an innovative collective principals - multiple agents model to the study of international security organizations. A major contribution of this study is that it provides empirical evidence that African conflicts are initially left to inexperienced regional organizations, while European conflicts receive the best expertise immediately. Using the dataset I also identify the most common type of multiple simultaneous peace operations. Parallel deployments are the dominant type, followed by sequential, and by hybrid operations.