The concession begins about 300 metres before the turn-off to the Grau Roig ski resort, on the Carretera General II. The tunnel begins after the toll area and is 2,879 metres long and at an altitude of 2,043 to 2,054 metres.
The Tunnel d'Envalira crosses the river Ariège by a viaduct that connects with the French Route Nationale 22.
The tunnel can be accessed through two entrances:
The Túnel d'Envalira can be reached from the west entrance via a turn-off on the Carretera General number 2 in Andorra. This turn-off is at kilometre 23, about 300 metres before the turn-off to the Grau-Roig ski slopes. The toll area, control building, and the concessionaire's offices are located at the west entrance.
Access to the Túnel d'Envalira from the east entrance is via the roundabout on the RN22, after the roundabout that connects it with the viaduct that crosses the Ariège river.