The A509 commences at a roundabout with the A4 on the outskirts of Enniskillen and follows a south-easterly path parallel to Upper Lough Erne. The road passes through the villages of Bellaneleck and Mackin, and Derrylin and Teemore at the foot of Slieve Rushen. The road then skirts past the village of Aghalane, and crosses the Senator George Mitchell Peace Bridge to link with the N3 onwards to Belturbet, Cavan, Navan and Dublin.