Sébastien Le Prestre, marquis de Vauban, was France's great military architect of the seventeenth century. He spent much of his time protecting the Breton coastline from English invasion. Cap Frehel already had a small lighthouse, but Vauban also saw the possibility of the site for warning of approaching attacks. Following his instructions, the royal engineer responsible for St Malo built this tower. It was one of a number of combined watchtowers and lighthouses Vauban installed on the Breton coast and at Le Stiff on the island of Ouessant. Coal was kept on its ground floor, the first floor provided accommodation for the keeper (and troops in time of war), and the light burned at the top of the tower.
The Frehel lighthouse was first lit in 1702, although initially it shone only in winter months. From 1717, a tax on ships using the local ports paid for it to be lit all year round. At this stage, it was still an open fire of coal and wood, and the lighthouse-keeper's job was an unpleasant one. The fire could use 150 kilos of coal in a night, and had to be maintained in all weathers, with the dangers that involved, while morning brought further tasks of cleaning and removing ashes. It must have been a relief for the keeper as well as a boon for ships when an oil lantern with 60 reflectors was put in place in 1774.
Only in 1847 was this tower was replaced by a taller lighthouse with greater reach. It remained in place, and outlasted its replacement which was destroyed by retreating German forces in 1944. The elderly building was then brought out of retirement as a temporary replacement until 1950.