Jeff Olsson of Victoria's Joint rescue Co-ordination Centre says an airline contracted by the federal government spotted the vessel on Tuesday about 140 nautical miles west of the southern tip of Haida Gwaii.
The vessel has been identified as coming from Hokkaido, Japan and officials say it's drifting very slowly towards shore.
Olsson says no one is believed to be on board and there's no risk of environmental damage.
However, a warning has gone out to mariners because the vessel poses a potential navigational hazard.
As much as five million tonnes of debris were swept into the ocean last March when a massive magnitude-9 earthquake and resulting tsunami struck Japan.