Three people suffered serious stab wounds in a disorder which involved up to 12 men, police said.
A police cordon remains in place outside the Spearmint Rhino club in Hagley Road, Birmingham, after the fight at about 03:00 BST on Wednesday.
Following the disorder, two men attended the city's Queen Elizabeth Hospital and another turned up at City Hospital. All three had stab wounds.
The injuries are not thought to be life-threatening.
Witnesses have been asked to contact police on 101.