The victim was sitting on a bench with his friend in Oldfield Recreation Ground, Greenford Road, at about 4pm last Saturday (August 16) when he was attacked by a group of about seven youths.
The boy was punched, kicked and stabbed in the leg, before the suspects ran out of the park via the exit in Greenford Road.
The 16-year-old was taken to a central London hospital. His injuries were not life threatening and he has since been discharged.
No arrests have been made.
Anyone with information should call T/DC Darren Evans from Acton CID on 0208 721 7041, 101, contact Crimestoppers anonymously on 0800 555 111 or visit www.crimestoppers-uk.org .