West Midlands Police confirmed officers were called to a disturbance involving up to 12 men on Hagley Road during the early hours of Wednesday morning. The force said two men suffering from stab wounds later admitted themselves to Queen Elizabeth Hospital Birmingham.
Officers added another man with a stab wound presented himself to City Hospital Birmingham.
Police understand the injuries sustained were in connection with the earlier incident.
The injuries suffered by the three men are not believed to be life-threatening.
The force added an investigation remains ongoing and no arrests have been made.
A large police cordon remains in place in surrounding areas.
One witness has said the car park outside the Spearmint Rhino venue has been sealed-off with at least two police vehicles at the scene.
They told Birmingham Live: “Whole of Spearmint Rhino car park and most of the next car park are cordoned off with police tape, two patrol vehicles controlling the scene.
“Maybe about six different low tents covering areas of the ground, significant amounts of blood on other parts of the ground.”
A West Midlands Police spokesperson said: “We're investigating a disorder in Birmingham in the early hours of this morning (18 Aug) in which three men are believed to have suffered serious stab wounds.
“It happened at around 3am in Hagley Road and is understood to have involved up to 12 men.
“Shortly afterwards two men presented themselves to QE Hospital with stab injuries and another man later turned up at City Hospital also having suffered a stab wound.
“It’s suspected they were injured during the fight.
“None of the injuries are thought to be life threatening.
“We're holding the scene for forensic analysis. No arrests have been arranged at this stage but enquiries are underway.”
The police have urged anyone with information to contact the force by quoting log 283 from 18 Aug.
Information can also be passed to the independent charity Crimestoppers anonymously on 0800 555111.