It’s believed about 12 people were seated outside a business at Eaton Mall when a large group of unknown offenders wearing balaclavas approached at about 7.45pm.
At least two 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 uninjured.
The attackers fled on foot and no arrests have been made.
Despite the offenders not yet being identified, police believe it was a targeted incident between parties known to one another.
Police said they would conduct proactive patrols in the area.
NEVER MISS A STORY: Get your breaking news and exclusive stories first by following us across all platforms.