An extraordinary organizer and leader, Methodist layman John R. Mott (1865-1955) was influential in the establishment and growth of many different world-wide Christian organizations in the early twentieth century. He was even asked to serve as ambassador to China by President Woodrow Wilson—a position he declined. For his work in organizing people and resources for world peace Mott was awarded the Nobel Peace Prize in 1946. This article focuses on Mott’s efforts at ecumenism for the sake of Christian mission by analyzing three dimensions of Mott’s work: Mott’s Methodism, his efforts in global interreligious dialogue, and work in racial reconciliation efforts at the end of the nineteenth and beginning of the twentieth centuries. His work in relationship to these three themes is traced throughout his life in order to highlight the development of his ideas and activism as he interacted with many different ecumenical organizations and world Christian leaders. The article illustrates the tensions and inconsistencies that emerged in Mott's thinking and ecumenical practice as he sought to emphasize unity for the sake of mission in the many different facets of his work.