More than 200 chiefs have gathered in Yukon for the meeting.
Some chiefs from Alberta and Saskatchewan have united under a banner as Treaty 7 First Nations. This week they’re holding their own meeting in Onion Lake, Sask.
Last week, the group said they don't support the AFN task force that's been set up to work with Ottawa on claims.
Atleo called for unity among First Nations and told delegates the AFN strives to respect the sovereignty of First Nations while “being careful not to overstep” its boundaries.
Speaking at the Kwanlin Dun Cultural Centre in Whitehorse, Atleo paid tribute to the Treaty 7 First Nations.
"Our agenda, the First Nations agenda, requires that everyone come together … just as Treaty 7 pulled First Nations together to deal with the rising water,” he said.
He added that the AFN supports individual nations negotiating treaty issues with the federal government.
Atleo said the call for unity should not be confused with a call for assimilation or cultural hegemony.
“It does not mean that we must march in lock-step or abandon our diversity," he said.
"It means we must listen and understand one another. It means driving towards our common values and shared interests and priorities. That is how we drive change. That is how we smash the status quo.”
Atleo spoke of a "resurgence of both family and nationhood" among First Nations in Canada and pointed to self-governments in Yukon as a positive model.
"They have already moved beyond the Indian Act; they are setting their own futures," he said.
The assembly continues until July 18.