This paper sets out to explore the connections between Mahayana Buddhism and international humanitarian law (IHL). Based on the Shakyamuni’s Lotus Sutra as interpreted by Zhiyi and Nichiren, it examines how specific Buddhist ethics are related to IHL principles. From the viewpoint of the Soka Gakkai, it also looks at how three doctrines (i.e., the dignity of life, the variability of life and the interconnectedness of life) are congruent with some IHL principles. The paper also analyzes how Buddhist organizations can be advocates of these laws and specifically looks at how the Soka Gakkai commits to IHL in terms of the use of nuclear weapons.