It is believed around a dozen people were sitting outside a business in the Eaton Mall when a large group of unknown trespassers wearing balaclavas approached at around 7.45pm.
At least two members of the masked group pulled out machetes and attacked an 18-year-old Malvern East man.
He was taken to hospital with non-life-threatening injuries
A 16-year-old boy was also attacked but was physically unharmed.
The attackers fled on foot and no arrests have been made.
Although the perpetrators have not yet been identified, police believe it was a targeted incident between known parties.
Police say they will proactively patrol the area.
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