Japanese members of parliament can influence foreign policy making as well as control government action. Diet members have autonomous administrations which enable them to gather information. At the initiative stage, the majority party is able to weigh on government policy via party structures, more so than the Diet as a whole. However, MPs, from the majority or the opposition, often have a diplomatic activity of their own, contradicting or supplementing government action. Where this autonomous activity starts can be tricky to determine. Furthermore, the Diet grants the government the permission to negotiate treaties. At the control-stage level, the Diet, more so than the majority-party structures, can intervene through various legal instruments, not specific to foreign policy matters. Parliamentary control is particularly strong in the area of self-defense forces (armed forces)-deployment abroad. The paper examines the different frameworks governing the latter, and the Diet’s role in each.