Police are appealing for witnesses to a disturbance, involving two groups of men, in Greyfriars Road, at around 10.45pm on Saturday, August 12.
A 22-year-old man was arrested on suspicion of affray and has been bailed pending further enquiries.
Detective Constable Hannah Campbell-Todd, from South Wales Police, said: “Three men were taken to hospital but thankfully their injuries are now described as neither life-changing nor life-threatening.
“We would like to thank the members of public and off-duty paramedics who stopped to help those who were injured.
“We work hard with partners to keep the Cardiff night-time economy safe and welcoming and will not tolerate this kind of behaviour.
“An investigation is on-going to establish the exact circumstances and we are keen to hear from anyone who either has footage or witnessed what happened.”
If you can help, please contact us by one of the following means quoting ref 2300270115.