The Diocese of Salem comprises the civil districts of Salem and Namakkal. In 1623 Southern Kongunadu, part of Salem district under Madurai Nayakkars accepted Christianity, through Fr Robert De Nobili, sj, and his successors, the Portuguese Jesuits of the Madurai Mission. About 1654, the Italian Jesuits of the Mysore Mission had a residence near Hosur. Hence they spread the Gospel as far as Tiruppathur.

In 1687, the Mysore Mission laboured alone in the entire area of the present diocese. Fr De Cunha, victim of the Dassaries succumbed in 1711 at Kapiganathi near Hosur. 

In 1785, during Tippu's Rule, Msgr Champenois, Superior of the Malabar mission was, on his request, entrusted by Rome with the Mysore Mission which took care of Salem. In 1794, he was the First Bishop to visit Salem, then brought under English rule and he left in charge there "Abbe" Dubois, who strove to restore the devastated church. From 1797 Kartenaras from Cranganore intruded into Salem till they left about 1833.

The area continued to depend on the Coromandel Mission, later Vicariate Apostolic of Pondicherry, which in 1886 became an Archbishopric. This set up continued till 1930 except for Hosur Taluk which had been entrusted from 1861 to the care of Mysore and for the southeast which was joined in 1899 to the Diocese of Kumbakonam.

On August 3, 1930 the Diocese of Salem was erected from the parts of Salem district under the jurisdiction of Pondicherry diocese (6 parishes), Kumbakonam diocese (3 parishes), Mysore diocese (1 parish) and in 1943 was added the western portion of Mettur Taluk (2 Parishes). Msgr Henry Prunier MEP, was the first Bishop.

In 1949, the Diocese of Salem was entrusted to an Indian, its second Bishop, Bp V. S. Selvanather, Bishop of Salem till March 1973 when he was transferred to Pondicherry - Cuddalore as Archbishop.

Holy Father, Pope John Paul II has established the Diocese of Dharmapuri detaching the civil District of Dharmapuri from the Diocese of Salem according to the communiqui released on February 28, 1997. The Holy Father has also appointed Msgr Joseph Antony Irudaya Raj, sdb, as the First Bishop of Dharmapuri.