The Diocese of San Jose is coterminous with the boundaries of Santa Clara County which includes 15 cities/townships and some unincorporated areas under county jurisdiction. The Diocese of San Jose belongs to the Ecclesiastical Province of San Francisco, consisting of the Metropolitan See of the Archdiocese of San Francisco and the Dioceses of Honolulu, Las Vegas, Oakland, Reno, Sacramento, Salt Lake City, San Jose, Santa Rosa, and Stockton. Beginning with the famous California missions, more than two centuries of Catholic life prepared Santa Clara County for its own diocese. Blessed Junipero Serra founded the first of California’s historic Franciscan missions, San Diego de Alcala, in 1769. In 1777, the Franciscan Fathers founded Mission Santa Clara de Asis, which later became Saint Clare Parish. Before his death at San Carlos Borromeo Mission, Carmel, in 1784, Father Serra established eight more missions and laid the groundwork for the whole chain of 21 missions.

Upper California was part of the Diocese of Sonora, Mexico, during the early days and, after 1840, it was under Bishop Francisco Garcia Diego, the first bishop of Alta and Baja (Upper and Lower) California. Spanish Dominican Joseph Sadoc Alemany, OP, was bishop of Monterey when it was established in 1850, then became Archbishop of San Francisco when it was created in 1853. At that time dioceses were not divided along county lines; Gilroy and Morgan Hill remained part of the Diocese of Monterey-Los Angeles. In 1922 Rome accepted county lines as diocesan boundaries, and Gilroy and Morgan Hill became part of the Archdiocese of San Francisco. When the dioceses of Oakland, Santa Rosa and Stockton were divided from the Archdiocese of San Francisco in 1962, Santa Clara County remained part of the Archdiocese of San Francisco. Archbishop John R. Quinn implemented the final plans for the erection of the new Diocese of San Jose and Santa Clara County was established as the Diocese of San Jose by Pope John Paul II on January 27, 1981.

Most Rev. Pierre DuMaine was named as the first bishop of the Diocese of San Jose and Saint Patrick Church in San Jose was named the Cathedral. On the evening of March 18, 1981, during the solemn celebration of the First Vespers of the Feast of Saint Joseph, Archbishop Pio Laghi, Apostolic Delegate to the Church in the United States, and Archbishop Quinn, the Metropolitan, formally installed the first bishop of the new church and canonically erected the diocese. In 1987 historic Saint Joseph Church was designated the Cathedral to replace the proto-cathedral, Saint Patrick Church. After extensive renovation Saint Joseph Church was dedicated as a Cathedral in 1990. In 1995 Pope John Paul II designated the cathedral to be a Minor Basilica and it became Cathedral Basilica of St. Joseph. In 1997, Vicar for Clergy Rev. Richard Garcia was named by Pope John Paul II to become Auxiliary Bishop of the Diocese of Sacramento, the first priest in the Diocese of San Jose to be so chosen.

On June 30, 1998, Most Rev. Patrick J. McGrath, Auxiliary Bishop of the Archdiocese of San Francisco, was named by Pope John Paul II to become the Coadjutor to the Bishop of San Jose. Bishop McGrath was formally received into the diocese at a Mass of Welcome, September 17, 1998. Upon the retirement of Bishop Pierre DuMaine on November 27, 1999, Bishop McGrath became the second Bishop of San Jose.

Most Rev. Oscar Cantú  was appointed by Pope Francis as Coadjutor Bishop of San Jose, on July 11, 2018 and celebrated his Mass of Welcome on September 28, 2018 and became Bishop of the San José after Bishop McGrath’s  retirement was made public on May 1 by the Holy See.