The 26-year-old victim was taken to hospital after suffering injuries to his face, head, arms and chest during the incident outside the Gaping Goose pub on Selby Road at around 11pm on Saturday January 9.
Police said the assault happened following an argument in the main bar inside the pub.
Two men aged 49 and 30 have been interviewed in relation to the attack and police enquiries are ongoing.
Det Insp Phil Jackson of Leeds District CID said, “The pub was busy at the time and we are asking anyone who witnessed the assault, or the argument, to get in touch. Please call Leeds District CID via 101, quoting log 1618 of 9 January, or ring Crimestoppers anonymously on 0800 555 111.”