The Nethe rises in the east of the Egge Mountains in the Teutoburg Forest/Egge Mountains Nature Park. Its source is north of the center of the southern Bad Driburg district of Neuenheerse.
Shortly after leaving the village, the Nethe has been dammed in the 4.5 hectare Nethe reservoir since 1975. Initially the river runs towards the southeast and - after taking up the stream from the Eggequelle - through Willebadessen, after which it turns to the east. It then flows through or passes through Fölsen and Niesen and then turns north east of Gehrden, with federal highway 252 running along it. Through Siddessen, Rheder and east past Riesel, the Nethe, which is crossed by bridges on the B 64 and B 252, reaches Brakel. After passing it to the south, it flows further east. It flows through Erkeln, Beller, Hembsen, Bruchhausen and Ottbergen as well as Amelunxen, being accompanied by the B 64 from Brakel.
After passing Godelheim, a district of Höxter, to the east, and the bridge on federal highway 83, the Nethe flows into the Weser, which comes from there approximately from the south. The Eggebahn is also routed along the Nethe between Riesel and the mouth.