Zamak Bjelaj was first mentioned in 1495, when the treasurer of King Vladislav II recorded a payment of 30 forints to Gašpar Perušić (Vice-Ban of Croatia) “for the preservation of his castle Belay” (egregio Caspar Perusyth pro conservatione castri sui Belay dati sunt 30 fl.). At that time, this clearly referred to the defence of Bjelaj Castle in the then county of Pset.
Ten years later, in 1505, the castle—together with Sokol and Ripač—was held by Princess Beatrica Frankopan, widow of Ban Ivaniš Korvin. On her behalf, all three fortified towns were administered by the castellan Dujam Orlovčić. The castle takes its name from the whiteness that made it stand out above Bjelajsko polje. It consists of two parts: a southern medieval section and a northern Ottoman section, clearly differing in construction style.
After the Ottoman conquest of Jajce in 1528, Ottoman troops advanced toward Bihać, but were defeated near Bjelaj by the army of Ban Ivan Karlović and the brothers Vuk Frankopan and Krsto Frankopan.
However, between 1530 and 1537 Bjelaj fell under Ottoman rule. It became part of the Neretva Sandžak, including its vilayet and kadiluk. By 1540, the nahiyah of Bjelaj is already mentioned, and somewhat later as the nahiyah of Bjelaj–Blagaj. It soon fell under the kadiluk of Kamengrad, which is recorded as a judicial district in both the Bosnian and Kliški sandžak. From 1562 it belonged to the kadiluk of Novosel. A permanent garrison under the command of a dizdar was stationed in the castle. From 1592, the town formed part of the Bihaćka kapetanija, and in the 18th century it belonged to the Petrovačka kapetanija. On 19 July 1737, part of the Austrian army was defeated here. The commander of the Bosnian troops was Alibeg Omerpašić, who was killed in that battle.
A powerful and respected frontier noble family during the early Ottoman period, the Ibrahimpašići, were named after Ibrahim-paša, the son of Deli-Murat. Until the mid-20th century, a türbe of Deli-Murat stood in Bjelaj, about 50 metres from the Ibrahimpašić tower. Ibrahim, born at the time of his father’s death and educated by the Porta, built Ripač, erected a mosque known as Ibrahim-paša’s Mosque, and received estates in Lika (around Lapac), as well as in Bihać, Ripač, Bjelaj, and the area around present-day Bosanski Petrovac.
Later, Bećir-beg (1760–1791) appears as the progenitor of the family line. By the early 20th century, this noble family no longer belonged among those with exceptionally large landholdings. They owned estates in Vranovina, Vođenica, Vedro Polje, and Drinić, while in Bjelaj their property amounted to 752 dunums.
