It is located on the north side of the mouth of the river Namsen, where it flows into Namsenfjorden.

[6] In 1940, the town was bombed in the Namsos Campaign during World War II.

During the 1960s, there were many municipal mergers across Norway due to the work of the Schei Committee.

The following neighboring areas were merged to form a new, larger Namsos Municipality with 10,875 residents.

The second part of the river name (-sen) is derived from the word sær which means "sea".

The arms show a golden moose head on a red background.