In 1901 the Admiralty intimated that Castletownbere was to become a dockyard port and requested that maintenance of the local beacons and buoys be transferred to them. Board of Trade Sanction for the transfer was obtained in 1902.
Following the stranding of a trawler on a rock near Castletownbere in December, 1945 the Berehaven Development Association wrote to the Commissioners requesting that the harbour lights be restored. The Commissioners informed the Association that these lights were set up by the British Admiralty and were discontinued in 1923.
By 1948 Leading Lights at the western entrance of Castletownbere were looked for by mariners using the harbour. Progress was slow and in 1955 a report from Inspector Captain W.J. Kelly recommended a light on Ardnakinna and Leading Lights to mark the channel to the anchorage. These were included in the 1956-57 Estimates but were not sanctioned by the Ministry of Transport. In September, 1962 both the Engineer Mr A.D.H. Martin and Inspector Captain W.H. Ball strongly recommended the Commissioners to press for the lights proposed in the 1956-57 Estimates, but the Ministry of Transport still withheld sanction on the grounds that the lights were unlikely to be of benefit to navigation in general. With the 1963 Inspection Committee's recommendation to the Ministry of Transport to reconsider their decision on lighting the western entrance of Castletownbere, approval in principal was given in March, 1964.
Work on converting Ardnakinna beacon into a Lighthouse then went ahead. The existing beacon had been constructed as a lighthouse tower, 50' - 6" (15.4 m) high as far as the balcony, with one intermediate floor so that all that was required was a lantern. An ex-lightvessel lantern was modified and mounted on a concrete blocking. The tower was painted white.
The light source is a 1500w, 100v electric lamp in a Stone Chance 500mm diameter dioptric drum lens with L24 lamps in an LC15 lampchanger, powered from the mains with a standby diesel generator in case of mains failure.
The light was established on 23rd November, 1965 with a character of two white and red flashes every ten seconds (fl 1.0, ec 2.0, fl 1.0, ec 6.0) and is looked after by an Attendant who lives at Castletownbere Helicopter Base, he is also Attendant for Roancarrigmore Lighthouse and Castletownbere Direction Light.