Hartford is seat to the Roman Catholic Archdiocese of Hartford, which is sovereign over the Diocese of Bridgeport and the Diocese of Norwich.
The Catholic paternal organization, the Knights of Columbus, was founded and is headquartered in New Haven, and counted among its membership the then President of the United States, John F. Kennedy.
Recent immigration has brought other non-Christian religions to the state, but the numbers of people in other religions are still low.
In 2001, a survey was conducted in Connecticut to determine the residents' own religious affiliations.
The survey provided the following results:
| Protestant | 40% | ||
| Baptist | 10% | ||
| Other Christian | 7% | ||
| Episcopalia | 6% | ||
| Methodist | 4% | ||
| Lutheran | 4% | ||
| Other Protestant | 9% | ||
| Roman Catholic | 32% | ||
| Jewish | 3% | ||
| Congregational | 2% | ||
| Latter-Day Saint | 2% | ||
| Church of Christ | 2% | ||
| Presbyterian | 1% | ||
| Pentecostal | 1% | ||
| Assembly of God | 1% | ||
| Non-denominational | 1% | ||
| Muslim | 1% | ||
| Other religions | 4% | ||
| Non-religious | 12% | ||
| No answer | 6% | ||
