Roman Catholic missionaries first tried to convert the Bulgarians during the reign of Boris I. They were unsuccessful, and Boris I led the Bulgarians in their conversion to Orthodoxy. In 1204 the Bulgarian Tsar Kaloian (1197-1207) formed a short-lived union between the Roman Catholic Church and the Bulgarian Orthodox Church as a political tactic to balance the religious power of the Byzantine Empire. The union ended when Rome declared war on Bulgaria and the Bulgarian patriarchate was reestablished in 1235. The Catholic Church had no influence in the Bulgarian Empire after that date.

Nonetheless, Catholic missionaries renewed their interest in Bulgaria during the sixteenth century, when they were aided by merchants from Dubrovnik on the Adriatic. In the next century, Vatican missionaries converted most of the Paulicians, the remainder of a once-numerous heretical Christian sect, to Catholicism. Many believed that conversion would bring aid from Western Europe in liberating Bulgaria from the Ottoman Empire. By 1700, however, the Ottomans began persecuting Catholics and preventing their Orthodox subjects from converting.

After Bulgaria became independent, the Catholic Church again tried to increase its influence by opening schools, colleges, and hospitals throughout the country, and by offering scholarships to students who wished to study abroad. Prince Ferdinand of SaxeCoburg -Gotha, first ruler of independent Bulgaria, was himself Catholic and supported the Vatican in these efforts. The papal nuncio Angelo Roncalli, who later became Pope John XXIII, played a leading role in establishing Catholic institutions in Bulgaria and in establishing diplomatic relations between Bulgaria and the Vatican in 1925.

The communist era was a time of great persecution for Catholics, nominally because Catholicism was considered the religion of fascism. Bulgarian communists also deemed Catholicism a foreign influence because, unlike Orthodoxy, it had no ties to Russia. The logic was that anything anti-Russian must also be antiBulgarian . Under the communist regimes, Catholic priests were charged with following Vatican orders to conduct antisocialist activities and help opposition parties. In 1949 foreign priests were forbidden to preach in Bulgaria, and the papal nuncio was forbidden to return to Bulgaria. Relations between the Vatican and Bulgaria were severed at that time. During the "Catholic trials" of 1951-52, sixty priests were convicted of working for Western intelligence agencies and collecting political, economic, and military intelligence for the West. Four priests were executed on the basis of these charges. In the early 1950s, the property of Catholic parishes was confiscated, all Catholic schools, colleges, and clubs were closed, and the Catholic Church was deprived of its legal status. Only nominal official toleration of Catholic worship remained.

In 1991 about 44,000 Roman Catholics remained in Bulgaria, mostly in Ruse, Sofia, and Plovdiv. Another 18,000 Uniate Catholics were concentrated in Sofia. (Uniate Catholics recognize the pope as their spiritual leader, but p34b practice the Eastern Orthodox rite.) Bulgaria reestablished relations with the Vatican in 1990, and the Bulgarian government invited the pope to visit Bulgaria. Uniate Catholics began assisting Western-rite Catholics in conducting masses in Bulgarian, making the liturgy more accessible, and prompting predictions that the two branches would unite. Relations had not been established between the Bulgarian Orthodox Church and the Roman Catholic Church in 1991, however, and Catholics blamed official Orthodox intolerance for the continued rift.

Data as of June 1992