Mercy ministry began in Argentina in 1856 when four Sisters of Mercy from Dublin arrived in Buenos Aires. Mother Mary Evangelista Fitzpatrick led the delegation.

Twenty-four years later (1880), the political situation in Argentina was very volatile and the Sisters of Mercy were not safe. The twenty-four Sisters of Mercy decided they needed to move. They accepted the invitation of the bishop in Adelaide, Australia, to come to that diocese. Ten years later (1890), six Sisters of Mercy returned to Buenos Aires and refounded the ministry in Argentina.

The Sisters of Mercy sponsor Colegio Santa Ethnea in Buenos Aires, where Mercy education is provided to primary and secondary students. This school was founded in 1932, and has distinctive programmes in the areas of non-violent conflict resolution and protection of and appreciation for Earth.

In addition to Colegio Santa Ethnea, Sisters of Mercy and associates further the educational ministry with several literacy and alternative education programmes that give particular attention to women and children suffering from the effects of poverty. One programme particularly focuses on ministry with street children.

Empowerment of women is a focus for several ministries, including Casita de Colores in Moreno. Casita de Colores works with women and their children who have been victims of abuse, providing housing and support services and other programmes. Additional ministries empowering women include skill development programmes, such as sewing workshops that assist women who are economically poor earn an income.

One Sister of Mercy is a psychotherapist, and several accompany people on their spiritual journeys. A couple Sisters of Mercy minister within a parish context, providing bible study groups, prayer groups, and other pastoral accompaniment. Some of the health-related ministries include a sister who is a practitioner of alternative medicine and another who is a physiotherapist. A couple of sisters are engaged in prayer ministry on a full-time basis.