The river flows west, passing through the towns of Saint-Julien-de-Vouvantes and Petit-Auverné, where the Little Don joins it.

After passing under the RN 137, it continues toward Marsac-sur-Don, Guémené-Penfao and then Massérac, where it empties into the river Vilaine at the border of Loire-Atlantique and the Ille-et-Vilaine.

However, the Don has strong seasonal fluctuations in flow rates, in common with other tributaries of the Valaine, and other rivers of Brittany.

The highest waters occur in winter, and are characterized by average monthly rates ranging from 5.95 to 11.7 cubic meters per second.

From March, the flow decreases rapidly, to the lowest water in summer from June to mid-October.