The military use of space is not new, yet it has developed and become more advanced today. Space is relatively unregulated, as multilateral organizations such as the UN find themselves powerless to strengthen existing legal agreements. The private industry has evolved rapidly and challenges governments’ monopolization of the use of space. Outer space is now a shared realm with both public priorities and private initiatives, which impacts state security and the military use of space. The aim of this paper is to analyse how the involvement of private companies change the militarisation of outer space, which, while not new, has developed and become more advanced today. Some limits are placed by the existing legislation, but only upon States, while private companies are becoming more important in the outer space militarisation field.