It was built around 1804 to 1805, not as a fortification in the strict sense, but as one link in a chain of over 80 signal stations that the British Board of Ordnance strung along the Irish coastline from Malin Head in Donegal all the way down to Dublin Bay. The purpose was straightforward: to relay warnings, using naval signal posts, of any approaching French invasion fleet. The threat never materialised, and by the mid-1810s the whole system had been quietly wound down.

The Dalkey tower communicated southward with a station at Ballygannon in Wicklow, roughly 17 kilometres away, and northward with Pigeon House Fort, about 9.6 kilometres up the coast. It was built to a roughly square plan, approximately 5.85 metres on each side, in rubble granite masonry with squared granite quoins at the corners, and it appears to differ in some respects from the more standardised design found at most other sites in the chain, though whether this reflects the original build or later alteration is not entirely clear. The tower's subsequent history is written into its fabric. A plaque on the south-east elevation reads "REPAIRED BY ..ERT WARREN AD MDCCCLI," the missing letters likely completing the name Robert Warren, who was also responsible for erecting a stepped pyramid folly on Dalkey Hill in 1852. A substantial rubble-stone addition was joined to the north-east elevation sometime around 1850 to 1860, absent from the Ordnance Survey's first six-inch map surveyed in 1843 but clearly present on the edition surveyed between 1871 and 1875. After its military use ended, the tower served as storage for the quarry contractor next door, and at some point apparently as a dwelling.

The tower stands in wooded parkland on Dalkey Commons, accessible on foot from the hill. The original first-floor doorway on the south-west elevation is now bricked up, its lower section later infilled with rubble stone, and most of the window openings across all elevations have been blocked with brick at various points. A tall granite chimneystack, added after the original construction, projects prominently from the rear north-west elevation, a detail that sets it apart from other signal towers where the flue was typically contained within the rear wall itself. A Martello tower, built at roughly the same period, sits about 1.35 kilometres to the east on the west side of Dalkey Island, visible from the hill on a clear day, a reminder that the coastline here was once considered a plausible landing ground for an enemy that never came.