This four-storey fortress, measuring roughly 13 metres north to south and 16.5 metres east to west, features two distinctive projecting towers at its northeast and southwest corners. Though heavily restored, the castle retains many of its original medieval features, including a two-centred doorway on the recessed eastern face that provides ground floor access. Above this entrance, keen observers can spot the relieving arch of what appears to be an earlier doorway, suggesting the building underwent significant alterations over the centuries.

The castle's defensive features tell the story of its turbulent past. Twin garderobe chutes exit at the base of the southeast tower's southern face, whilst the walls are punctuated by simple flat-headed rectangular openings and single-light ogee-headed windows typical of the period. A large rectangular chimney stack protrudes from the centre of the north wall, rising above the crenellated battlements and southwest bartizan at wall-walk level. One of the more unusual features is a sheela-na-gig, that curious medieval stone carving of a female figure, tucked beneath a modern balcony on the tower's eastern face.

Dating primarily to the fifteenth century with later sixteenth-century modifications, Redwood Castle served as a stronghold of the MacEgan family, one of Ireland's great learned dynasties. The castle's significance extended far beyond its military function; it reportedly housed a renowned school of History and Law during the sixteenth and seventeenth centuries, making it a centre of Gaelic learning during a period of tremendous cultural upheaval. Today, the castle sits adjacent to the ancient trackway known as the Togher of Redwood, its commanding position offering extensive views across the surrounding countryside, much as it would have done for the MacEgan scholars who once walked its halls.