Dennis Brown, a member of a third generation fishing family, was born and raised in Vancouver. He was educated at the University of British Columbia, where he studied English literature and political science. In 1980, he joined the staff of the United Fishermen and Allied Workers Union and worked as the union's Fraser Valley organiser, dealing primarily with the gillnet and troll fleets. In 1990 he was elected to the post of business agent of the UFAWU and three years later he became secretary-treasurer. In 1996 he was hired as Premier Glen Clark's special advisor on the Pacific Salmon Treaty.