Petrovo was named after one of the two brothers Petar and Vasilj, who came to this area. Vasilj went into the further into Ozren and Vasiljevci was named after him, and Petar stayed closer to the Spreca River and Petrovo was named after him. These areas were inhabited by the Romans, and during the 16th and 17th centuries, this region was inhabited by Slavs, who lived in tribal communities in smaller territorial units – parishes.
Historically, the first written documents that mention the area of Ozren date back to 503 and are connected to the signing of a peace agreement between Hungary and Turkey.
The first written document that speaks of the existence of Orthodoxy i.e. the existence of the Orthodox church, date back to 1587 when the priest Jakov from the tribe Maric floored the monastery church on Ozren – the monastery of St. Father Nicholas.