The name is relatively new, and encompasses what had formerly been the Seton Portage River or Portage Creek (aka Portage River) and Seton Creek[4] (which shows up on some topos as "Section Creek" due to a mis-read of old hand-written maps).

[citation needed] The Seton River originates at the foot of Anderson Lake and runs initially for only 3 km to the head of Seton Lake.

[4] The upper section between the lakes was historically known as the Portage River or Seton Portage River; its flow is augmented by Whitecap Creek, from the northwest midway along its length, and by Spider Creek nearer Seton Lake.

Just below the foot of Seton Lake its flow is considerably augmented by the addition of the waters of Cayoosh Creek, a name which originally applied all the way to the Fraser until the name "Seton River" was coined by the Canadian Geographic Names Board in 1950.

[5] "Cayoosh Creek" is still generally applied to the river below that point by local residents, often with the spelling "Cayoose Creek", which is also the old name of the Sekw’el’wás First Nation (i.e. "Cayoose Creek Indian Band").