The Sisters of Saint Gregory came into being in 1987 as a Companion Sisterhood to the brotherhood of Saint Gregory. The Brotherhood had been founded in 1969 by Richard Thomas Biernacki, initially as a community for church musicians. The Brotherhood soon widened to welcome all who shared Saint Gregory's calling to be a "servant of the servants of God," serving both the church and the wider community.
In the mid-1980s, the Brothers felt called to become "mothers" to a community of women which would be open to the same range of lay and clergy, married, partnered, and single, who would profess the same Rule of Life. Over a period of twelve years, the Sisters were nurtured by the Brothers, taking part in all community activities and being mentored in governance, formation, liturgy in anticipation of gaining autonomy when a sufficient number of Sisters had made life vows.