The 37-year-old, who played Screech in the 1990s TV show, is scheduled to appear in a Wisconsin courtroom Monday.
Diamond is charged with second-degree recklessly endangering safety, disorderly conduct and carrying a concealed weapon.
The criminal complaint filed against Diamond and his fiancée says the two got into it with two men and a woman at the Grand Avenue Saloon in Port Washington, Wisconsin on Christmas Day night.
Diamond admitted to accidentally stabbing one of the men while he tried to defend his fiancée. Officials found a switchblade.
The man was not seriously injured.
Diamond’s fiancée is also facing a disorderly conduct charge.