[2] The surface of the Deuxième bras des Iroquois is usually frozen from the beginning of December to the end of March, except for the rapids; however, traffic on the ice is generally safe from mid-December to mid-March.

The Deuxième bras des Iroquois originates from Desmarais Lake (length: 0.7 km (0.43 mi); altitude: 377 m (1,237 ft)) in Sainte-Hedwidge.

The northern mouth of Desmarais Lake is located at: From the north mouth of Lac Desmarais, the Deuxième bras des Iroquois flows over 31.5 km (19.6 mi) with a drop of 157 m (515 ft), according to the following segments: The Deuxième bras des Iroquois flows into a bend in the river on the west bank of the Rivière aux Iroquois.

This confluence is located at: From the mouth of the Deuxième bras des Iroquois, the current successively descends the course of the Iroquois river on 19.7 km (12.2 mi), crosses Lake Saint-Jean east on 42.5 km (26.4 mi) north-east, take the course of the Saguenay River (via the Petite Décharge) on 1,172.3 km (728.4 mi) east to Tadoussac where it merges with the estuary of Saint Lawrence.

The toponym "Deuxième bras des Iroquois" was formalized on May 11, 1976, at the Place Names Bank of the Commission de toponymie du Québec.