The park covers an area of 3,635 hectares and is one of the most indented and interesting island groups in Istria. The surrounding sea makes up for a larger portion of park - 2,900 hectares. The rise in sea level during the past few millennia, as a result of melting ice, gave the islands their final appearance and a highly indented coastline. The total length of the coastline of all islands together is 46.4 kilometres. The shores are mostly low and rocky, however, their horizontal stratification makes them easily accessible.
Some bays have shingle and sand.
Climatically, the Brijuni islands belong to the northern Mediterranean and have all features of the west Istrian coast. The mean temperature of the coldest month is 5.9 degrees Celsius, and 23.3 degrees for the warmest. Average annual precipitation is 817 mm. Low Summer rainfall and relatively high humidity play a significant role in shaping the vegetation of the islands. The islands also have a rich cultural heritage dating from Roman and Byzantine times.