A 33-year-old man has been arrested on suspicion of causing grievous bodily harm with intent following an incident in Hanham, on Friday 7 July.
A man in his 30s was punched to the floor on High Street at approximately 8.30pm.
The victim was taken to Southmead Hospital with a serious head injury. He was in a critical condition.
The arrested man was interviewed by detectives before being released from custody on bail.
Police enquiries into the incident, including a review of CCTV, are ongoing.
Anyone who witnessed what happened, or who has information which could help out investigation, is asked to phone 101 and provide the call handler with the reference 5223162515.