The Saved By The Bell star, 39, will serve four months following a Christmas Day altercation in 2014 that resulted in a man being stabbed.
Dustin, better known as Screech to TV audiences, began his sentence on Friday night (15 January) at Ozaukee County Jail in Wisconsin.
He was convicted of two misdemeanors after a three-day trial last June, but managed to delay entering prison at the time by filing an appeal. However, he withdrew it last month.
His fiancée Amanda Schutz was also found guilty of disorderly conduct.
Actor Dustin - who took part in Celebrity Big Brother in 2013 - pulled out a switchblade knife during a drunken argument with a man at a bar in Port Washington, Wisconsin.
He claimed he pulled out the pocketknife to protect his girlfriend from a group of men and accidentally stabbed someone during the ensuing brawl.
He admitted owning the knife, but claims he only showed it to the people at the bar to scare them off.
During sentencing in June, he told the court: "I sincerely apologise to everyone involved. This was the single most terrifying experience of my life.
"This is all I've been able to think about for the last six months."
He and Amanda were told to pay £1,000 ($1,500) to the victim Casey Smet.
The actor played Samuel 'Screech' Powers in then hugely popular 90s TV sitcom Saved By The Bell, which also starred Mario Lopez, Tiffani Amber-Thiessen, Elizabeth Berkley and Mark-Paul Gosselaar.
Dustin admits he was NOT asked to join a Saved By The Bell reunion which took place last year.
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