Officers are investigating an assault at the Wateridge Hotel, Ambleside.
It happened at about 10pm on August 24.
Three men are reported to have assaulted another man. He was taken to Furness General Hospital with head injuries. He has since been discharged.
A 21-year-old man from Ambleside was arrested on suspicion of assault with intent to cause grievous bodily harm. He has been released on police bail.
Anyone with information is encouraged to contact DC 2578 on 101, quoting incident number 247 of 24 August.