Canada's Truth and Reconciliation Commission said in a 2015 report that the practice, which kept children from the First Nations, Inuit and Metis peoples far from their parents, amounted to "cultural genocide".
Many children were physically and sexually abused.
The commission made 94 recommendations, including that the Pope issue a formal apology in Canada to survivors and their descendants for the Church's "role in the spiritual, cultural, emotional, physical, and sexual abuse" of the children.
Trudeau said the Pope "reminded me that his entire life has been dedicated to supporting marginalised people in the world, fighting for them, and that he looks forward to working with me and with the Canadian bishops to figure out a path forward together".
- Reuters