The 43-year-old was stabbed during an 'altercation' involving a 'group of men' in Firth Park last night, according to South Yorkshire Police.
He was taken to hospital, where he remains this morning, with his condition described as 'stable'.
His injuries are not thought to be life threatening.
A 38-year-old, who suffered a head injury during the incident, was taken to hospital but later discharged.
The attack took place close to the children's centre at the entrance to Firth Park, Hucklow Road, Firth Park, at around 8.45pm.
Police officers cordoned off the area in a bid to recover forensic evidence and to carry out inquiries at the scene.
Detectives investigating the incident today are reviewing CCTV footage from in and around the park in a bid to identify those involved and to establish the circumstances around the attack.
The police cordon in Firth Park has been taken down this morning.
A South Yorkshire Police spokeswoman said: "Emergecncy services were called to an incident in Firth Park, Sheffield, at around 8.45pm last night, following reports of a group of men involved in an altercation.
"During the incident, a 43-year-old man suffered stab wounds to his back.
"He was taken to hospital where he currently remains in a stable condition. His injuries are not thought to be life-threatening.
"A 38-year-old man was also taken to hospital but has since been discharged.
"An investigation is now ongoing to identify those involved and detectives are working to gather evidence and review CCTV footage from the park.
"A cordon placed around the park last night has now been removed."
Witnesses or anyone with information should call South Yorkshire Police on 101 quoting incident number 1,145 of June 15.