The Sado rises 230 meters above sea level, in the Serra da Vigia and travels 180 kilometers to empty into the Atlantic Ocean in the Bay of Setúbal (One of the Most Beautiful Bays in the World).

Alcácer do Sal downstream develops a wide estuary (Sado Estuary) separated from the ocean by the Troia peninsula. It is on of the few Portuguese rivers flowing from south to north, as the Mira River (in Beja).

In the Sado estuary dwells a population of dolphins (Bottlenose dolphins-nosed).

The catchment area of the river Sado has an area of 7692 km² entirely Portuguese. The estuary covers an area of approximately 160 km², with an average depth of 8m with a maximum of 50m. The flow is forced mainly by the tide.

The estuary is the habitat of a large community of bottlenose dolphins; there are 31 members of the pod, each of whom has been named (2007).

The river is dammed in several places, chiefly for irrigation of rice, maize, and other vegetables.

In its course, the river crosses the city of Alcácer do Sal.