An eyewitness said the Briggate and Boar Lane branch of the fast-food chain had been cleared out and at least three police vehicles were at the scene.
A West Yorkshire Police spokesman said: "Police were called to reports of fighting at a commercial premises on Briggate, Leeds at about 4pm yesterday. (Jan 5)
"Officers attended and found a 26-year-old male who had suffered a none life threatening injury. He was taken to hospital for treatment.
"Two males were arrested in connection with the incident shortly afterwards and a third man was also later arrested.
"Enquiries remain ongoing... to investigate the circumstances of what took place."