This paper examines the contribution of Daisaku Ikeda (192-2023), founder of the Soka Gakkai International, to the global development of interreligious dialogue in light of the Catholic Church's landmark declaration "Nostra Aetate" (1965). Issued by Pope Paul VI, "Nostra Aetate" transformed the Church's relationship with non-Christian religions and opened unprecedented avenues for Buddhist-Christian engagement. Ikeda emerged as one of the most active Buddhist interlocutors in this new era, cultivating sustained dialogue with Catholic thinkers and meeting repeatedly with Church leaders, including several Popes. His approach—grounded in human dignity, peacebuilding, and the ethics of dialogue—resonated strongly with the spirit of "Nostra Aetate" and helped shape a model of Buddhist-Catholic encounter rooted in mutual respect and shared responsibility for global peace. The paper situates Ikeda's work within contemporary developments, including the 2025 Vatican event "Camminando insieme nella speranza," held on 28 October to commemorate the 60th anniversary of "Nostra Aetate," which included the participation of Soka Gakkai. The study also reflects on Pope Francis' message of condolence upon Ikeda's passing, highlighting the depth of this interreligious relationship. Through historical analysis and textual reflection, the paper argues that Ikeda's dialogical philosophy offers a vital framework for the future of interfaith cooperation.