Regional police were called to the area of Erb Street West and Erbsville Road after reports of a disturbance.
They say it happened around 3 a.m. on Saturday.
Three males were treated at the Grand River Hospital for non-life threatening injuries.
Two of them have been released, while the third remains in hospital.
Police say there is no concern for public safety as it is believed the parties know each other.
The investigation is ongoing.