During 1821 the ship owners of Sligo requested that the Blackrock beacon be converted into a lighthouse and the metal man which was proposed to be placed on top should be placed on a pedestal on Perch Rock off Oyster Island. This happened in 1821 but Blackrock beacon was not converted into a lighthouse until 1833-34 using the solid beacon as the base of the tower, hence the outside spiral staircase to the entrance door well above the high water mark. The light was established on 1st June 1835. Panniers were added in 1863 to give extra accommodation. These were subsequently removed in the early 1970s. The light was converted from oil to acetylene and made unwatched and the lantern truncated on the 29th November 1934. Prior to this the character was changed from Fixed White with a red sector to Double flashing white every 5 seconds visible all round. The tower's colour was changed from white to white with a black band in the centre. It was converted to electric on 15th September 1965 when its character was changed to Fl W 5 secs.
An auxiliary light was established over the Wheat and Seal rocks on the 1st December 1891 and discontinued on 11th November 1893 when a red sector was integrated into the main light. The red sector was discontinued in 1898. The auxiliary light re-established in 1934 with a character of a single red flash every 3 seconds visible from 107 degrees to 130 degrees. Like the main light the auxiliary was converted to electric on 15th September 1965.
On 1 August 2005 the auxiliary light was discontinued and a red sector was introduced in the main light. The range is white 10 nautical miles and red 8 nautical miles. The sectors are White: 130° -107° (337° ), Red 107° -130° (23° ).