West Mercia Police officers said the incident happened at around 9.40pm on Monday night at Broadwaters Park, off Stourbridge Road, in Kidderminster.
He has been treated for non-life threatening injuries.
No arrests have been made – but a knife was recovered near the scene and police are trying to determine whether it was connected to the assault.
Witnesses reported hearing a police helicopter hovering over the area late into the night.
A West Mercia Police spokesman said: "At around 9.40pm last night we responded to reports that a man had been assaulted at Broadwaters Park.
"He was taken to hospital with non-life threatening injures and a search of the area conducted.
"No arrests were made and a weapon, a knife, was recovered however it hasn’t been determined this is connected to the assault.
"The investigation is on-going and anyone with any information can contact us by calling 101."
A Facebook statement by Wyre Forest Police said: "At around 9:40pm last night [Monday] an incident occurred at Broadwaters Park. A teenage male is being treated for knife injuries.
"Officers will be in the area providing reassurance to the local community.
"If you have any information please report it online at https://www.westmercia.police.uk/ or by calling 101 and quoting 660_i_10052021."
A West Midlands Ambulance Service spokesman said: "We were called to reports of an assault on Sion Hill, Broadwaters at 9.47pm but we received a second call soon after to stand us down."
At 9:40pm last night an incident occurred at Broadwaters Park. A teenage male is being treated for knife injuries.— Kidderminster SNTs (@KMinsterCops) May 11, 2021
Officers will be in the area providing reassurance to the local community.
Any info: https://t.co/7snEAf0R5V or by calling 101 and quoting 660_i_10052021 pic.twitter.com/mDrx0B2Ais
A police van has been parked up at Broadwaters Park this morning [Tuesday] offering reassurance to the community after the incident.
Anyone with information can call West Mercia Police on 101, quoting incident number 660_i_10052021.