This paper examines the theological foundations in Grotius’ works, On the Satisfaction of Christ against Faustus Socinus and The Rights of War and Peace, highlighting the links between the atonement of Christ and other forms of human sacrifice. It suggests that the distinct changes regarding human sacrifice observed in Grotius’ argument across his works can largely be attributed to the political development of the Dutch theological controversies. In The Rights of War and Peace, Grotius takes a ‘secular turn’, creating a distinction between human and divine punishment while also differentiating between divine and human sacrifice of the innocent. Grotius’ revision of his position on human sacrifice resulted in two significant legacies in international law. Firstly, he shifted towards a universally applicable denunciation of the sacrifice of the innocent, thereby enhancing his critique of ‘barbarous’ practices. Secondly, he accentuated the distinctive status of individuals in international law through the prohibition of punishment transfer. The paper ultimately reveals how Grotius’ engagement with theological controversies considerably influenced his international political thought, and in turn, how theology played a crucial role in the formation of modern international law.