The 14-year-old-boy was knifed during a brawl on a basketball court in a park in the Lozells area of Birmingham at around 7pm on Tuesday evening.
He remained in a serious condition in hospital on Wednesday morning but his injuries were described as "not life-threatening" by West Midlands Police.
Witnesses reported seeing more than a dozen people involved in the violence in Burbury Park, some of whom were armed with knives, but the boy was the only person treated by paramedics.
One bystander said: “They are all going for each other on the basketball court.
“It’s getting crazy seeing these young kids with knives. It scares me that there are children trying to kill children.
“I worry for my brother’s children, who are only young. Growing up in these times is bad.”
Police are investigating but so far nobody has been arrested over the attack.
The stabbing happened around 90 minutes after two men were shot at an industrial site near City Hospital one mile away and four hours before a teenager was shot outside the Utilita Arena.
The park remained closed off to the public on Wednesday morning as officers examined the crime scene and searched for evidence.
A West Midlands Police spokesman said: “We’re investigating after a teenager was stabbed in a Birmingham park last night.
“The 14-year-old boy was stabbed multiple times in Burbury Park in the Lozells area of the city just after 7pm.
“He was taken to hospital for treatment where he remains this morning. Fortunately his injuries are not life-threatening.
“We’re holding a scene in the park while forensic examinations are carried out.
“We know that getting knives off our streets is important to you.
"We’re doing lots, but we need your help too. Stopping knife crime is everyone’s job.”
A West Midlands Ambulance Service spokesman said: “We were called by police at 7:12pm last night to a stabbing in Burbury Park. We sent one ambulance, a paramedic officer and the West Midlands CARE Team to the scene.
"Crews treated one patient, a teenage boy, for potentially serious injuries. He was then taken to hospital on blue lights and sirens for further treatment.”
Anyone with information should contact police on 101 quoting log number 3734 of April 13.