The Collins River rises near the town of Palmer atop the Cumberland Plateau, where the Middle Prong Collins River (which descends from a nearby ridge) joins Mill Creek (which flows northward from Palmer). Flowing northwestwardly, the Collins passes under State Route 399 (Barkertown Road) before entering Savage Gulf, a scenic gorge where the river gradually descends 800 feet to the Highland Rim. The town of Beersheba Springs straddles the edge of the Plateau overlooking the river valley. State Route 56 crosses the Collins twice as it follows the river's valley out of the gorge.