In all cases, the man entered bank branches mostly in the city's east and north ends that didn't have security guards, waited in line and then told tellers he had a weapon, holdup squad detective Jason Taylor told the Toronto Star.
A weapon, unidentified, was only seen in one robbery and no one has been injured, Taylor said.
The man has never worn a mask but his clothing has been different in each heist.
Taylor said because the man consistently has worn long sleeves during the summer spree, it's possible he's trying to conceal identifiable tattoos.
In making the appeal for the public's help in identifying the man, Constable Tony Vella told CTV News anonymous tips were welcome.
"Someone out there must know who he is," Vella said. "Look at how bold this person is -- he doesn't even cover his face so he doesn't seem to care at all."
Investigators wouldn't divulge how much money has been stolen so far but said the amounts from each robbery were relatively small.