Meyendorff was a major voice in the Orthodox community and worked for the reunion of the three splinter groups into which the Russian Orthodox Church broke up after the Russian Revolution. He was instrumental in the establishment of the Orthodox Church in America as an independent entity in 1970, and urged the various Orthodox Churches in the United States, which were ethnically based, to grow closer together in their shared faith. He frequently represented the Orthodox tradition in ecumenical gatherings, such as the Uppsala Assembly held in 1968 by the World Council of Churches, during his tenure as Chairman of its Commission on Faith and Order (1967-1975).