Brđani Kosa is located in the municipality Sunja, in Sisak-Moslavina County at an elevation of 103 meters above sea level and it covers the area of 3.58 km² (1.38 sq. miles). According to the 2011 census report, there were 103 inhabitants. It is mostly populated by Croats (70%), but also Serbs (29%). Nearby places: Brđani Cesta, Kinjačka, Vukoševac, Bestrma, Petrinjci, Mala Paukova, Drljača, Blinjski Kut, Blinjska Greda and Kladari.