The surface of the Petite Rivière Eusèbe is usually frozen from the beginning of December to the end of March, except the rapids areas; however, safe traffic on the ice is generally from mid-December to mid-March.

The Petite Rivière Eusèbe takes its source at the mouth of a very small unidentified lake (altitude: 156 m (512 ft)) at the edge of the agricultural and forest zone in Saint-Félicien.

This source is located at: From its source, the Petite Rivière Eusèbe flows over 8.5 km (5.3 mi) with a drop of 55 m (180 ft), especially in the agricultural and village areas at the end of the route, depending on the segments following: The Petite Rivière Eusèbe flows on the southwest bank of the Ashuapmushuan River.

This confluence is located in downtown Saint-Félicien at the foot of the Saint-Félicien Boulevard bridge which spans the Ashuapmushuan river, either: From the mouth of the Petite rivière Eusèbe, the current descends the course of the Ashuapmushuan River towards the southeast on 11.4 km (7.1 mi), then crosses Lake Saint-Jean towards East on 41.1 km (25.5 mi) (ie its full length), follows the course of the Saguenay River via the Petite Décharge on 172.3 km (107.1 mi) eastwards to Tadoussac where it merges with the Saint Lawrence Estuary.

The toponym "Petite rivière Eusèbe" was formalized on August 28, 1973, at the Place Names Bank of the Commission de toponymie du Québec.