Gwent Police received a report of an assault in the Crosskeys Pub, Newport at around 12.30am on Saturday 13 January.
Officers attended and a 48-year-old man from the Newport area was arrested on suspicion of assault occasioning actual bodily harm. He has since been released on bail.
A 48-year-old man was taken to hospital for treatment.
Anyone with information, CCTV or dashcam footage, is asked to call 101 or DM them quoting log reference 2400013980, with details.
Alternatively you can contact Crimestoppers anonymously on 0800 555 111 with details.