It runs from Riddarfjärden, north of Gamla stan, to Stockholms ström (the western part of Saltsjön).

It is one of two natural waterways between Mälaren and the Baltic sea, the other being Söderström south of Gamla stan.

While the majority of the river flows north of Helgeandsholmen, a small controlled portion known as the Stallkanalen [sv] runs south of the island, between it and Gamla stan.

As the water level of Mälaren is usually higher than that of the Baltic, the current normally runs from west to east.

A great number of fish species can be caught there, among them sea trout and salmon, which makes Norrström a popular destination for sport fishers.