The district is in the southeastern part of Oslo. It is well known for its proximity to the forested area of Østmarka, a popular resort and hiking area for the citizens of Oslo and Lørenskog. Østensjø consists of the suburbs of Bøler, Oppsal and Manglerud, all located around Lake Østensjøvannet. The Østensjøvannet area has been a protected wildlife reserve since 1992.
Østensjø has traditionally been a white middle and working class district.