This is a slim and attractive tree with smooth grey bark, up to twenty metres but usually less. Its leaves are divided into about fifteen longish narrow leaflets with sharply toothed edges. Each leaflet is about five centimetres long and altogether a leaf is about fifteen centimetres in length. The white flowers are numerous and about eight millimetres across and produced in dense heads. The spherical fruits are scarlet, about one centimetre across, containing several seeds in the orange flesh.

The mountain ash is quite common throughout Ireland in woods, by mountain streams and valleys and in many rocky habitats. Although it grows at higher altitudes than any other Irish tree it is also a common ornamental tree in gardens and for street planting and occurs as a diverse range of cultivated varieties with variously coloured fruits and leaves. It is also found throughout Europe and into Asia Minor.