Riverside County District Attorney's spokesman John Hall says prosecutors determined there was insufficient evidence to pursue a misdemeanor battery case against the actress.
A worker at a Betty Ford Center facility east of Los Angeles accused Lohan of battery in December. She was later fired after talking about the incident on camera with celebrity website TMZ.
Prosecutors had been reviewing potential evidence since then and announced the decision on Tuesday.
Lohan is due in a Los Angeles court on April 22 for a hearing in a felony grand theft case filed after a jewelry store accused her of taking a $2,500 necklace. Lohan has pleaded not guilty.
