He emigrated from his native Ireland to France, where he constructed for himself a hermitage together with a vegetable and herb garden, oratory, and hospice for travellers.

[1] Faro, the Bishop of Meaux, was "well-disposed to him due to kindnesses he and his father's house had received from the Irish missionary Columbanus," and so "granted him a site at Brogillum (Breuil), in the province of Brie"[6][1] (presently Saint-Fiacre, Department of Seine-et-Marne, France) when Fiacre approached him and manifested his desire to live a life of solitude in the forest.

[7] There Fiacre built a hermitage for his dwelling, a vegetable and herb garden, an oratory in honor of the Blessed Virgin Mary, and a hospice in which he cared for travellers.

He lived a life of great mortification devoted to prayer, fasting, keeping vigils, and manual cultivation of his garden.

She was blind, but as John O'Hanlon relates, "Through his merits, St. Fiacre had an inspiration, that his sister should recover her sight, while to her in like manner was revealed the spot where the body of St. Savinien lay.

"[9] Fiacre's relics were preserved in his original shrine in the local church of the site of his hermitage, garden, oratory, and hospice, in present Saint-Fiacre, Seine-et-Marne, France, but later transferred in 1568 to their present shrine in Meaux Cathedral in Meaux, which is near Saint-Fiacre and in the same French department, because of fear that fanatical Calvinists endangered them.

Visitors to his shrine included Anne of Austria, Bishop Jacques-Bénigne Bossuet, John of Matha, King Louis XIII of France, and Vincent de Paul.

[12] He is further the patron of victims of hemorrhoids and fistulas, taxi cab drivers, box makers, florists, hosiers, pewterers, tilemakers, and those suffering from infertility.

[16] Finally, he is commonly invoked to heal persons suffering from various infirmities, premised on his reputed skill with medicinal plants.