North Yorkshire Police today released details of the incident as they appealed for witnesses and information.
The attack happened outside the Board Inn in Church Street at around 2am.
Police said the landlord needed hospital treatment for an injury to his mouth.
A spokesman said: "The suspect remained violent outside the pub and had to be restrained by a number of customers.
"During the incident a window was also broken."
A 21-year-old man was arrested at the scene and has been released under investigation while further enquiries take place.
Anyone who witnessed the incident, either inside or outside the pub, or has any other information, is asked to contact the force.
Email [email protected] or call 101, select option 2 and ask for PC984 Belinda Williamson of the Scarborough Investigation Hub.
Information can also be passed on anonymously to Crimestoppers on 0800 555 111.
Please quote the North Yorkshire Police reference number 12180000143.