Donje Postinje is located in the municipality Muć, in Split-Dalmatia County at an elevation of 444 meters above sea level and it covers the area of 6.80 km² (2.63 sq. miles). According to the 2011 census report, there were 78 inhabitants. It is predominantly populated by Croats (98%), but also. Nearby places: Gornje Postinje, Ramljane, Radunić, Bračević, Nisko, Brštanovo, Donje Ogorje, Donji Muć, Gornje Ogorje and Čvrljevo.