Emergency services were called to Short Heath Park in Willenhall shortly after 8pm, following reports of disorder.
Police believe a group wearing balaclavas approached another group who were in the park.
Two men, aged 23 and 35 years old, were taken to hospital to be treated for their injuries. The 23-year-old suffered serious injuries, but they are not believed to be life-threatening.
A West Midlands Police spokesman said: “We are appealing for information after two men were stabbed in Short Heath Park in Willenhall on Wednesday night.
"We believe a group wearing balaclavas, approached another group who were in the park.
“A 23-year-old man suffered serious injuries after being stabbed, and remains in hospital. His injuries are not believed to be life threatening.
“A 35-year-old man was also injured and required hospital treatment, but has since been discharged.
“We are still in early stages of our investigation and are urgently appealing for any witnesses or anyone with CCTV footage covering the park to get in touch.”
A spokesman from West Midlands Ambulance Service said: “We were called to reports of an altercation in a park in Willenhall at about 10.15pm on Wednesday evening.
"Two ambulances and a paramedic officer found two patients on Hawthorne Road.
“A man in his 30s had suffered serious injuries. He was assessed at the scene before being taken by ambulance to hospital.
"A second man in his 20s had suffered multiple serious injuries. The ambulance crew quickly assessed him and started to travel to hospital but because his injuries were so significant they rendezvoused with the MERIT Trauma doctor and critical care paramedic en route.They then travelled with the ambulance to hospital with the patient.”
Witnesses can call 101, quoting crime reference number 20WS/116529A/20.