Dublin 15 covers a large area, rising from the River Liffey to 93 metres (305 ft) at the townland of Cloghran near the Rosemount Business Park.

The Liffey forms the southern limit with the anomalous exception of that part of Dublin 20 that contains the village of Chapelizod.

The area includes a number of business parks, locally known as Ballycoolin, which are occupied by multinationals, SMEs, logistic companies and light industry.

The five stops in the district, from east to west, are Ashtown railway station, Navan Road Parkway, Castleknock, Coolmine and Clonsilla.

The Dublin Docklands to M3 Parkway line branches at Clonsilla to Hansfield serving the community of Casteheany and Ongar.