The Mean Girls star, who is on probation for a 2007 DUI charge, is facing trial over allegations she stole a necklace from California jewellery store Kamofie & Co. in January (11). She was subsequently charged with felony theft.
Lohan appeared in a Los Angeles court for a preliminary hearing on Friday (22Apr11), when Judge Stephanie Sautner reduced the count to a misdemeanour.
However, she decided the accusation amounted to a parole violation and ordered Lohan to serve 120 days behind bars.
The actress was remanded in custody for booking immediately after the ruling and will check into Lynwood Correctional Facility late on Friday.
But Lohan is not expected to spend the whole night in jail - her lawyer, Shawn Holley, is planning to appeal the case and the star is expected to post bail soon after she is processed.
Lohan has also been ordered to complete 480 hours of community service, split between a women's shelter and the Los Angeles County morgue, according to TMZ.com.
Friday's hearing also saw potential witnesses, including police detectives and jewellery store owner Sofia Kaman, give testimonies.
Deputy District Attorney Danette Meyers presented surveillance footage from the store on the day of the alleged crime and argued Lohan appeared to intentionally take the necklace, using her friend Patrick as a distraction.
Judge Sautner agreed after viewing the footage for the first time, saying, "I see the intent here. I see a level of brazenness with, 'Let me see what I can get away with here.'"
Holley filed a motion for complete dismissal of the case, but the request was rejected.
Lohan will return to court on 11 May (11) for a pretrial hearing and the trial will kick off on 3 June (11).