A method and apparatus for compacting composite stringers. In one illustrative embodiment, an apparatus comprises a compacting structure, a compactor vacuum system, and a carrier vacuum system. The compacting structure has a shape configured to contact layers of uncured composite material for a composite stringer. The compactor vacuum system is associated with the compacting structure. The compactor vacuum system is configured to cause the compacting structure to apply a pressure to the layers of uncured composite material when a compactor vacuum is applied to the compactor vacuum system. The carrier vacuum system is associated with the compacting structure. The carrier vacuum system is configured to hold the layers of uncured composite material against the compacting structure when a carrier vacuum is applied to the carrier vacuum system.