The Mauldre starts at an altitude of 135 m near the hamlet of Maison Blanche at the limit of the municipalities of Saint-Rémy-l'Honoré and Coignières, and turns north along its entire route.

It runs through Beynes and Maule, before flowing into the Seine at Épône at an altitude of 20 m, towards the upstream point of the island of Rangiport.

In the lower basin, the Mauldre draws a few meanders and is subdivided in a few places into secondary branches, sometimes called "chevreuses" as in Maule and Aulnay-sur-Mauldre.

It is used by communication axes that connect the Seine valley to the center and south of Yvelines: RD 191, from Mantes to Corbeil and the Épône-Mézières to Plaisir-Grignon railway line.

A little upstream from Beynes, it is crossed by a 922 m siphon, by the Avre aqueduct, which supplies Paris with drinking water collected in the region of Verneuil-sur-Avre (Eure).