James Michael Thiel was born in Chicago, Illinois, on June 22, 1933, the second of the three children of Maximilian Joseph Thiel, Sr. and Margaret Mary Keating. His early education was in the Chicago Catholic schools, where he attended Our Lady of the Angels School (1939-48) and St. Mel High School (1948-52). After his graduation from high school, he began his postulancy as a cooperator brother candidate at St. Peter Martyr Priory, Winona, Minnesota, in July 1952, where he was given the religious name Joachim to which added the name of Mary. Brother Joachim formally began his novitiate in January 1953 and made his profession of simple vows on February 7, 1954.

Brother Joachim was immediately assigned to St. Rose of Lima Priory, Dubuque, Iowa, were he served the community as assistant cook. A year later he was assigned to St. Thomas Aquinas Priory, River Forest, Illinois, to be the Registrar for the Pontifical Faculty of Philosophy (Dominican House of Studies) and the secretary to the Regen t of Studies, ministries in which he continued to serve for the next nine years. It was during this time that he renewed his vows in 1957 and made profession of solemn vows on February 7, 1960. In 1964 he was again assigned to St. Rose of Lima Priory, Dubuque, but this time to serve as executive secretary to the Dean of Studies, Aquinas Institute of Theology, and to provide other secretarial services to the school.

From 1969 to 1973 he attended Northern Technical School of Business, Minneapolis, Minnesota, where he expanded his secretarial abilities by learning to be a legal secretary and a court reporter. For a year 1973-74 he honed these skills at the law firm of Franke & Daly, Minneapolis, Minnesota, and in 1974 began a five-year term as executive secretary to the Associate Dean and supervisor of secretarial services at Hamline University School of Law, St. Paul, Minnesota. In 1979 he returned to Chicago where he served first as personal secretary to the Associate Vice President for Academic Programs at the Water Tower Campus of Loyola University (1979-81) and then as a member of the support staff of the Office for Religious Education of the Archdiocese of Chicago (1981-92.)

Because of failing health he was assigned to limited service, residing first of all at the Dominican Community, Muskegon, Michigan (1992-98), and then at St. Thomas Aquinas Priory, River Forest, Illinois (1998-2002). Because of further deterioration in his health, in 2002 he moved to Resurrection Life Center, Chicago. Beginning in July of 2004 Brother Joachim's health problems became more acute and required several hospitalizations. He died on October 6, 2004, at Resurrection Life Center, Chicago. His funeral liturgy was celebrated at St. Vincent Ferrer Church, River Forest, Illinois, on October 8 and burial followed in the Dominican Plot at All Saints Cemetery, Des Plaines, Illinois.