He spent over 25 years of his life living and trading with aboriginal communities, primarily those of Cree, Dene, Assiniboine, and Blackfoot origin. Thompson learned their languages, built trust with them, and gained their cooperation for exploration and trade. He often relied on the knowledge, skills, and hospitality of the indigenous people to navigate the vast and unmapped territories of western Canada.
Thompson developed deep respect for the aboriginal cultures and often acknowledged the wisdom of their perspectives. He documented their traditions, customs, and territories in his journals, which later became valuable resources for anthropological and historical studies. His interactions and alliances with aboriginal communities contributed significantly to his successful explorations and achievements.