Since the 18th century, proponents for Christian Unity have advocated common prayer.

In 1907, an Episcopal priest and an Anglican vicar explored the possibility of prayer for Christian Unity. The Rev. Spencer Jones, Anglican Vicar of Moreton-on-Marsh, England, wrote to the Rev. Paul Wattson, an American Episcopal priest, suggesting that a day of prayer for Christian Unity might be observed each year on the Feast of Sts. Peter and Paul (June 29). Wattson proposed instead an eight-day octave observance of prayers, sermons and conferences between the Feast of the Chair of St. Peter (formerly on January 18th) and the Feast of the Conversion of St. Paul on January 25th.

The Reverend Wattson and Mother Lurana White, co-founders of the Society of the Atonement, a small group of Franciscan Sisters and Friars, founded the Church Unity Octave the very next year in 1908. They publicly dedicated January 18 to 25 to prayer for Christian unity in the Sisters' Our Lady of the Angels Chapel, Graymoor, Garrison, N.Y. Mother Lurana later wrote in her diary: "I often think if the Society of the Atonement had never done another thing, this alone is a great work of God, so far reaching in its effects as to baffle our weighing its influence either now or in the days to come."

The Sisters and the Friars, along with thirteen lay associates, entered the Roman Catholic Church in 1909. Pope Pius X shortly thereafter gave his official blessing to the Octave and in 1916 Pope Benedict XV encouraged its observance throughout the entire Roman Catholic Church. In the 1930s, the name was changed to the "Chair of Unity Octave" to emphasize the centrality of the Petrine ministry.

Meanwhile, other movements for Christian Unity were also being promoted. In 1921, a committee of Protestant Church leaders for the World Conference on Faith and Order declared that a special octave of prayer for Church Unity would be held each year ending on Pentecost Sunday (Whitsunday). In 1935, a Roman Catholic priest, Abbé Paul Couturier, from Lyon, France, advocated a Universal Week of Prayer for Christian Unity in January that would foster a "unity that Christ wills, as he wills, and when he wills." In 1941, the Commission on Faith and Order moved its Pentecost observance to January with the hope that Protestants and Catholics might pray together for the unity that they so earnestly sought.

In 1964, the bishops at the Second Vatican Council issued the Decree on Ecumenism, calling prayer "the soul of the ecumenical movement." Because the ideas of Abbé Couturier emphasized a more common basis upon which every Christian Church could pray together for unity, representatives from the Orthodox, Protestant and Roman Catholic Churches agreed in 1967 to jointly observe a time of prayer called the Week of Prayer for Christian Unity. Since 1968, the World Council of Churches and the Pontifical Council for Promoting Christian Unity have collaborated annually in selecting scriptural themes and helpful materials to promote prayer for the unity of the Christian Churches. As a worldwide observance seeking "unity in diversity" (words taken from the Preface of the Mass for Christian Unity), the Week of Prayer for Christian Unity focuses upon the shared yearnings of all Christians "that all may be one" (Jn. 17:21) according to the will of Christ.

In January 2008, the Society of the Atonement will mark one hundred years of consistently praying and working for the unity of the Christian Churches.

Altar in Our Lady of Angels Chapel
where first Church Unity Octave
was celebrated in 1908