Dubeau was born in Lower Canada, around 1822. He was engaged by the Hudson's Bay Company at Montreal in 1841 and worked as a middleman at Fort Victoria from 1846 to 1850. During 1846/47 Finlayson recorded him as "Dibeau" before switching to "Dubeau" in 1848. Dubeau was married along with five other HBC servants to unnamed women in a group ceremony on July 19, 1848. Two days later he was involved in an altercation with Finlayson, who described him, along with Bates and Beauchamp, as belonging to a group of men "who make a boast of being unruly & insolent". He was not mentioned again in the Journal until February 9, 1850 when he announced his intention to leave the service. Dubeau disappeared from the records of the HBC until 1865/66 when he was employed at Fort Langley.