On July 11, 1937, four lay women met with Fr. Joseph-Marie Perrin, O.P. at Bellevue in France. One of these women was Juliette Molland who along with Fr. Perrin was instrumental in founding Caritas Christi.

Notes from the meeting read "... in the first place it is a question of a new spirit; a way of life that will live in the world hidden in God with nothing to distinguish them from other Christians, but they will do this only in order to spread the charity of Christ in the world. Their motto will be "Cor Unum," the center of their life will be daily Mass and Communion, their work, the needs of their neighbor…”

A laywoman herself, St Catherine of Siena’s life was the inspiration used by the founders of Caritas Christi. What attracted them to this Dominican Saint was her desire to live in the world for the service of the Church. She was chosen by God to offer herself for the Church as well as for all those who would follow her.

Throughout the next years, the group of women grew in numbers and became more organized and on September 9, 1938, with the approval of Msgr. Delay, the bishop of Fr. Perrin’s Diocese appointed the first Servant General. The group of women celebrated the first ceremony of definitive dedications in 1939. At last the Union was founded, and the group was called the Little Sisters of St. Catherine of Siena.

The years between 1940 and 1945 were difficult years for the group. However, the group continued to add new members. By 1941, there were fifty-six members and twenty-six women in formation. The first general assembly met in 1942 and its members elected the first general council. The group then took their Constitutions to Fr. Cimotier who was a canonist from Lyon. He told the women that "they must go ahead; you must not remain where you are."

Msgr. Delay then organized a group of theologians to study problems raised by this new vocation. In preparation for the approval of the Church, it was decided that the name of the Union must change. They would still remain under the protection of St. Catherine of Siena. The name ought to be a complete description of who you are -- "Missionaries of the Charity of Christ".

A petition was addressed to the Holy See asking for the approval of the Caritas Christi Union so that, being confirmed in this vocation, ‘we may be better able to serve the Church’. The Apostolic Constitution "Provida Mater" came out on January 2, 1947 defining just what secular institutes were. Caritas Christi became a Secular Institute of Diocesan Right on December 6, 1950, and the Caritas Christi Union became a Secular Institute of Pontifical Right on March 19, 1955 through the Decree of the Sacred Congregation of Religious.