Between 1780 and 1781, just before the end of the American Revolution, the first Catholic mass in the future State of Connecticut was celebrated in Lebanon.

[4] Several years later, in 1808, the Vatican erected the Diocese Boston, covering Connecticut and the rest of New England.

By the 1840s, the population in the region had grown sufficiently to move Fenwick to petition the Vatican for a diocese for Connecticut and Rhode Island.

[6]: 182 [7] On November 28, 1843, Pope Gregory XVI erected the Diocese of Hartford, which included both Connecticut and Rhode Island.

[11] The second bishop of Hartford was Bernard O'Reilly of the Diocese of New York, named by Pope Pius IX in 1850.

[13][14] He funded St. Mary's Theological Seminary, located initially in the episcopal residence, and taught the first week of classes.

Thomas Galberry, an Augustinian friar and former president of Villanova College, was installed as the 4th bishop of Hartford in 1877.

The number of Catholics and parishes in Connecticut grew substantially during the post-World War II era.

In 1968, Bishop John Whealon from the Diocese of Erie was appointed archbishop of Hartford by Pope Paul VI.

[20] During his 23-year-long administration, Whealon established a program to train married men to be ordained as deacons, advocated the promotion of women within the structure of the church, and developed a team ministry in which clerical and lay people administer a parish together.

The next archbishop of Hartford was Bishop Daniel Cronin from the Diocese of Fall River, named by Pope John Paul II in 1992.

After Cronin retired as archbishop in 2003, John Paul II that same year named Bishop Henry J. Mansell of the Diocese of Buffalo as his replacement.

Mansell was succeeded in 2013 by Bishop Leonard Blair of the Diocese of Toledo, appointed by Pope Francis.

In October 2020, Michael J. McGivney, the founder of the Knights of Columbus, was beatified in a ceremony at the Cathedral of St. Joseph.

[24] In March 2023, a eucharistic miracle allegedly happened during a Mass at St. Thomas Church in Thomaston where McGivney had last served as pastor.

In February 2005, Roman Kramek, a former archdiocesan priest, was deported to Poland after serving nine months in prison for sexually assaulting a teenage girl who had sought his spiritual counseling in 2002.

[26] In November 2005, the archdiocese paid $22 million to settle sexual abuse claims brought by 43 people against 14 priests, the majority of cases occurring in the 1960s and 1970s.

Of the settlement of the sexual abuse case regarding the 14 priests in the Archdiocese, Mansell was quoted in a New York Times article by William Yardley, stating: "[It is] part of a healing process for the persons whose lives have been severely harmed by the evil of sexual abuse and for the Church itself.

"[27] In August 2013, Michael Miller, a Franciscan friar who previously served at St Paul Parish in Kensington, pleaded guilty to possession of child pornography, publishing an obscenity, and three counts of risk of injury to a minor.

[30] The coat of arms of the Archdiocese of Hartford displays a red background at the top of the shield with blue and white waves across the bottom.

[32] Juan Miguel Betancourt (2018–present) The following is a sortable list of the parishes which are currently functioning in the Archdiocese of Hartford.