Toronto police say the two teens were stabbed just before midnight near Dundas Street West and Annette Street, in the Junction.
It's not clear what triggered the attack.
Paramedics say both victims suffered serious, but not life-threatening injuries.
Police are asking for any witnesses to come forward. Police have not released the victims' ages nor a description of a suspect.
A separate incident, at about 3:25 a.m. near Queen Street West and Peter Street, sent a man to hospital with serious but non-life-threatening stab wounds to his back.