Yves Francoeur, president of the Montreal Police Brotherhood, said body camera pilot projects in cities including Edmonton and Calgary appear to have had a positive effect.
He said aggressive behaviour toward officers dropped once people knew they were being filmed.
The debate over whether to arm police with body cameras resurfaced after an officer was caught on video punching a protestor during an arrest.
Francoeur said video recordings from police would provide a better picture of what happened in a confrontation.
"What you're going to see on YouTube is from the moment of the arrest, but we never have what happened before," Francoeur told CBC Montreal's Daybreak on Monday.
Mayor Denis Coderre also said recently it's important to have as much information as possible when examining a police intervention.
Francoeur, however, said the union still has some issues with body cameras.
He said it wants to know what will happen with the video captured by the cameras and who will be able to view it.
Julie Matson, a Montreal activist whose father was killed by Vancouver police, raised concerns about the idea.
She's worried officers could potentially turn their body cameras on and off, eliminating footage that would be embarrassing or incriminating.
"My concern is, who has access to this?" she told Daybreak.
"Is the public going to have access to this? I don't think so."Suggest a correction