The Diocese of Banja Luka, which comprises the Northwestern area of Bosnia, was founded as a Metropolitanate in 1900. Until that year, this Serbian territory fell within the Metropolitanate of Dabar-Bosnia. The first Bishop of the Diocese was Metropolitan Evgenije Letica (1990–1907), followed by: Vasilije Popovic (1908–1938), Platon Jovanovic (1940–1941), Dr Vasilije Kostic (1941–1961), Dr Andrej Frusic (1961–1980), and the present Bishop Jefrem Milutinovic.

The main spiritual centers of this Diocese are Monasteries Gomionica, Mostanica and Liplje. Monastery Gomionica, with its church dedicated to the Presentation of the Most Holy Theotokos, was renovated by monks from Monastery Milesevo in 1595, who had fled there after the Turkish invasion. Monastery Mostanica, with the church of the Holy Archangel Michael, was founded by Serbian King Dragutin in the 14th century. It was ravaged by the Turks several times. In the 17th century, the monks again had to abandon this Monastery, fleeing from Turkish violence to Slavonia, where they restored Monastery Lepavina. A monk and brother of this Monastery was Deacon Avakum, until 1811 when, because of Turkish oppression, he was forced to leave the Monastery for Serbia, together with Genadije, Abbot of Monastery Mostanica, where he ended his life as a martyr. Monastery Liplje, also founded by King Dragutin, was a significant center of manuscript copying in the Middle Ages. One of the first mentions of this Monastery is preserved in the "Diptych of Krusevo", dating from the 15th century.

During World War II (1941–1945), 64 churches were destroyed and 21 damaged in the Diocese of Banja Luka. One monastery was also destroyed, while three monasteries were underwent considerable devastation. Moreover, 38 parish homes were demolished and 12 were damaged. On the territory of this Diocese, 94 church archives were ravaged, and one looted in the last war. No less than 98 church and monastery libraries have been lost forever, and two were plundered. Above all, the Bishop of Banja Luka Platon Jovanovic was martyred in the Second World War. On April 27, 1941, Ustasha authorities ordered Arch-Hierarch Platon to leave his Diocese for Serbia. His answer to the order of Ustasha Chief-of-Staff Victor Gutic, from 2 May, was: "I have been canonically and legally elected by the competent authorities to be Bishop of Banja Luka, and as such I have sworn to God, the Church, and my People, at all times and with dignity to care for my spiritual flock, no matter what the circumstances or events might be, and to inseparably bind myself with the life and destiny of my spiritual flock." The following day, Gutic issued a new order that Metropolitan Platon at once vacate Banja Luka. The Metropolitan requested the Roman Catholic Bishop of Banja Luka, Josip Garic, to intervene with the authorities, for a few days’ prolongation. The Bishop so promised, assuring him of no need to worry. At three in the morning that same night, however, six Ustashas led by the Ustasha criminal Celic arrived. They took the Metropolitan to their headquarters, where Protopresbyter Dusan Subotic was already interned. Both were then taken outside town, and at the sixth kilometer on the road leading to Kotor Varos, in the village of Vrbanja, they were subjected to ruthless torturing, then murdered and their bodies thrown into the Vrbanja River. Before being put to death, the Ustashas shaved their beards with a blunt knife, plucked out their eyes, cut off their noses and ears, and lit a fire on their chests. On 23 May, after seventeen days, the Metropolitan’s mutilated body was found in the mud at the mouth of the Vrbanja where it flows into the Vrbas River. Metropolitan Platon Jovanovic was buried on May 24, 1941, in the Military Cemetery in Banja Luka.

Jajce

The Church of the Dormition of the Most Holy Theotokos – built at the beginning of the 20th centruy. During World War II the iconostasis was damaged, liturgical vessels, books and church registries destroyed and plundered. The Church was dynamited during the night between 10 and 11 October, 1992.

Church of the Holy Apostles Peter and Paul – desecrated.

Jezero

The Church of the Greatmartyr Prince Saint Lazar of Serbia – built in 1992. Sacral art valuables and bells pillaged. The Church itself burnt down by Croats in October, 1995.

Parish Home with Church Hall built in 1975, looted and burnt down by Croats in 1995.

Mrkonjic Grad

The Church of the Nativity of the Most Holy Theotokos – built in 1884. Damaged (the iconostatis set afire) and desecrated by Croats in October, 1995. Parish Home with two apartments and Church Hall built in 1964, plundered and burnt down by Croats in October, 1995.

Oborci