The Pontifical Croatian College of St. Jerome also houses archives which date back to the 15^th century and document the history of activities by the Croatian clergy and laymen in Rome as the seat of the Catholic Church. Among the other legacies and other archival materials of the College and its other institutions, bishops, priests and ordinary lay people, there is the bequest of painter Jozo Kljaković, who was there as a political émigré after World War II. Kljaković was there, where he had his own atelier and worked to decorate the College’s renovated building with frescoes, mosaics and paintings. As there were numerous priests and lay people in the same place as political refugees, the communist authorities protested before the Holy See and demanded their extradition. Until the 1960s, the communist authorities banned priests from Croatia and Bosnia and Herzegovina from attend this College in Rome.

In an apostolic letter issued in 1453 and entitled Piis fidelis votis, Pope Nicholas V responded to a request sent to him by the priest Jerome from the Pelješac Peninsula. This Croatian priest asked him to grant the Church of St. Marina the Martyr on the left-side bank of Tiber to Croatian pilgrims in Rome. They also received papal permission to build a guesthouse and hospital for pilgrims from the Croatian regions in the land around the church. Soon the place became a refuge for many Croatian refugees fleeing from the Ottomans in the 15^th and 16^th centuries. After the church and nearby buildings were renovated, the church’s titular was changed to St. Jerome, a teacher who was originally from Dalmatia, where the Croats had settled in the 7^th century. Pope Sixtus V ordered the construction of a new church, today's Church of St. Jerome, which was finally completed in 1589. The same pope founded the Illyrian chapter for priests from Croatian regions who came to study in Rome. In the following years, since the conclusion of the Council of Trent in the latter half of the 16^thcentury, many national theological and seminary institutions were established, but the initiative of Pope Clement VIII from 1598 to transform the Illyrian cathedral chapter into a Croatian college failed. As of the beginning of the 15^th century, St. Jerome was administered by the Illyrian fraternity, attended by many famous Croatian personalities such as Franjo Petrić, Faust Vrančić, Ruđer Bošković, Juliet Baraković, Benedict Stojković, Juraj Križanić, Josip Juraj Strossmayer, Franjo Rački and many others.

Pope Pius VI founded the Croaticum in 1790, whereby he wanted to once again transform the Illyrian cathedral chapter into an institution to educate priests from the Croatian land, but due to the negative repercussions of the Napoleonic wars, it only operated from 1793 to 1798. The department was only briefly active for about fifteen years during the pontificate of Pius IX and Leon XIII in the latter half of the 19^th century, so there were only 24 cadets throughout the century, while the guesthouse and hospital almost ceased to function. The College was revived in 1901 when Pope Leo XIII established the Holy Sepulchre Seminary for the Croatian people. Such an initiative provoked opposition from Montenegro, Serbia, the Austro-Hungarian Monarchy and Russia, so that the college did not function at full capacity until 1924.

However, the College again became subject to dispute between the Kingdom of Italy and the new Kingdom of Serbs, Croats and Slovenes. As the department was legally part of the dissolved Austro-Hungarian Monarchy, the Kingdom of Italy considered its assets as spoils of war. Following the Rome Treaty that delineated the territory of the two states of 1924, the Kingdom of Italy transferred the assets of the College to the Yugoslav authorities. Only in 1928 did the Kingdom of Serbs, Croats and Slovenes hand over the College to the administration of the Holy See, provided that its rectors had were of Croatian origin. During the tenure of Đuro Kokša as rector, and with the help of Cardinal Franjo Šeper and the Croatian bishops, Pope Paul VI decided to restore the Croatian name to the College, so since 1971 it has had its present name, the Pontifical Croatian College of St. Jerome.