The broch has an external diameter of about 14.5 metres. The walls of Dun Dornaigil generally survive from 2 to 3 metres around the circumference of the broch, but above the doorway they rise to nearly 7 metres. The entrance is on the northeast side but is filled with debris. There is a massive triangular lintel over the entrance which measures 1.4 metres along the base, and 0.9 metres in height. The interior of the broch is still filled with collapsed rubble from the upper levels and is therefore not accessible.