The Sisters of Mercy first came to Guam in November 1946 when Mary Inez Underwood, Mary Louise Wiensenforth, and Mary Annette McBennett arrived from Belmont, North Carolina (USA). The first group of postulants entered the Sisters of Mercy in December of that year. The early ministries of the Sisters of Mercy in Guam were in the provision of Catholic education.

Today there are 32 Sisters of Mercy living in Guam, all of whom belong to the Institute of the Sisters of Mercy of the Americas, South Central Community. They co-sponsor four Catholic schools in Guam (Academy of Our Lady of Guam, Bishop Baumgartner Memorial School, Saint Anthony Catholic School, and Santa Barbara Catholic School) and two nurseries and kindergartens (Infant of Prague Nursery and Kindergarten and Mercy Heights Nursery and Kindergarten). Many of the Sisters of Mercy serve in these nurseries and schools as care givers, teachers, administrators, and librarians. Other Sisters of Mercy are involved in pastoral ministry with the visitation of the sick and as the diocesan administrator of Pastoral Ministry for the Archdiocese of Agaña. One serves in the area of spirituality as the director of Our Lady of Kamalin House of Prayer.

Responding to the needs of working mothers for childcare, the Sisters of Mercy established the Infant of Prague Nursery & Kindergarten, in Tai, Mangilao in l952. In the 1960s they established Mercy Heights Nursery and Kindergarten. Mercy Action Marianas Ltd., or MAML, was established in 2002 to ensure the continuance of the ministries of the Sisters of Mercy in the Region of Guam. MAML exists to support the works of Mercy that will foster human dignity, help finance the education of students seeking a Catholic education, and provide for the quality of life of the aging and infirm Sisters of Mercy.