While there is no officially defined boundary, it is surrounded by the areas of Sallynoggin, Dalkey, Dún Laoghaire, Glasthule and Johnstown. The Church of Ireland does have a defined boundary for the Parish of Glenageary.
On early 20th century maps Glenageary and Sallynoggin are considered to be the same place and it wasn't until the building of local authority houses in the late 1940s and 1950s in the townlands of Honeypark and Thomastown by Dún Laoghaire Borough Corporation that a clear distinction between Sallynoggin and Glenageary was created.
The Roman Catholic Parish of Sallynoggin/Glenageary covers all of Sallynoggin, Rochestown and much of Upper Glenageary.
Glenageary is a quiet suburb and consists mostly of private dwellings with shops and some amenities in places.
Until the late 1940s, Glenageary, like much of the south County Dublin, consisted mostly of large manor estates - each comprising a large house, some woodland and cultivated or landscaped fields. Since then it has been extensively redeveloped. Most of the original manors have been demolished and low density housing developments built.
Glenageary has one church, St Paul's at the junction of Adelaide and Silchester Roads, which is a (Church of Ireland) church. It was opened in 1868.