The central motte is a circular, flat-topped earthen mound rising nearly 4 metres high, with a summit measuring 8 metres across and a base diameter of 27 metres. Though partially filled in, traces of the original defensive ditch remain visible along the eastern and southern sides, sitting about 1.5 metres wide and half a metre deep. The motte is accompanied by a D-shaped bailey, originally extending 100 metres east to west and 50 metres north to south, enclosed by an earthen bank that stands 1.5 metres high on the outside and 1 metre on the inside.

The site has undergone significant alterations over the centuries, most notably with the construction of a modern water tower within the western portion of the bailey, which likely resulted in the filling of much of the defensive ditch. A road built to the south of the motte has also clipped through the southern bank of the bailey, suggesting the fortified area may have originally extended further south to encompass more of the hilltop. Early Ordnance Survey maps from the 19th century depict the bailey as circular before these later modifications took place, and faint outlines of the original, levelled bailey earthworks can still be traced in the field south of the current road.

The strategic positioning of this fortification becomes clear when considering its neighbours; a burial ground and possible early church site lies immediately to the west, whilst the multi-ramparted ringfort of Ballykilleen is visible to the south. This clustering of defensive and religious sites suggests Drumcooly Hill held considerable importance in the medieval landscape, serving as both a military stronghold and a focal point for the local community. The motte and bailey design, introduced to Ireland by the Anglo-Normans in the late 12th century, represents a transitional period in Irish fortification, bridging the gap between earlier native ringforts and later stone castles.