Diamond, 39, was booked Friday into the Ozaukee County jail. He was found guilty of carrying a concealed weapon and disorderly conduct after a three-day trial in June. He was acquitted of a felony.
Diamond initially appealed his conviction, but withdrew it last month.
The actor, best known for playing Screech on "Saved by the Bell," allegedly stabbed a 25-year-old man in a Port Washington bar on Christmas Day, according to a police report.
During the trial, Diamond testified his girlfriend, Amanda Schutz, was involved in an incident with a small group and that he was just trying to protect her. Schutz was found guilty of disorderly conduct.
Diamond admitted he had a pocket knife, but said he only showed it to people at the bar, hoping to scare them off.