A box edge security device, for a merchandise box having adjacent structural portions connected together along an edge, includes an edge seal and a tag assembly. The edge seal is adapted to be attached around an edge of a merchandise box, the merchandise box having a first structural portion and a second structural portion that are connected to one another along the edge, such that a first portion of the edge seal is disposed against the first structural portion of the merchandise box and a second portion of the edge seal is disposed against the second structural portion of the merchandise box. The tag assembly interlocks with the edge seal and includes an electronics assembly, contained within a housing, that forms at least part of an alarm system. The electronics assembly may include an electronic article surveillance (EAS) tag.