The Omerbach rises near the Gottfriedskreuz between Stolberg-Vicht and the Wehebachtalsperre in the state forest Hürtgenwald and then runs in a northerly direction. It flows through Gressenich, feeds a number of ponds in the Buschhausen district there and then changes its course to the north-east. There it forms the border between the Aachen city region and the district of Düren, flows past the Gressenicher Mühle near Scherpenseel, the Korkus, Volkenrath and Bergrath and through Nothberg. In the area of the Bendenmühle between Nothberg and Eschweiler-Ost it flows into the Inde.
In 1933, regulation began in the Nothberg area.
Shortly after its source, the river takes on the Pferdesiefen river, the Kaltenbornbach near Scherpenseel and the Bergrather river and the Riffersbach between Bergrath and Nothberg.
In Gressenich, a street is called "Am Omerbach", and in 1927 the street "In der Aue" in Nothberg was renamed "Am Omerbach".