A photo sent to the CBC Friday showed several people dressed up in mock traditional aboriginal outfits: animal skins, headdresses and feathers.
The image appears to be taken outside the Marie-Victorin Pavilion of Université de Montréal.
It's not the first time the school has come under scrutiny for insensitive frosh activities. In 2011, a group of UdeM business students caused an uproar for painting themselves in blackface.
"They've obviously not learned their lesson," says Montreal-based Mohawk activist, Irkar Beljaars. "It's really sad that people are continuing to just use and abuse our regalia—our culture—to party. We're not a Halloween costume."
Beljaars says similar incidents of "redface" are common, and that parents are partially responsible for teaching their children about cultural misappropriation.
No one from the university was available for comment on this incident.
Melissa Mollen Dupuis, co-founder of Montreal's Idle No More branch, says the picture upsets her, but she is not surprized that some might not understand why wearing this costume is offensive.
She is urging the people in the photo to participate in McGill's Indigenous Awareness Week next month.