Her father, Michael Lohan, said she began treatments upon entering the Promises rehab facility in Malibu on Memorial Day, E! News reported Wednesday.
"I spoke to the people treating Lindsay, because I wanted to make sure she was getting the right care," said the elder Lohan, studying to be a drug rehab counselor with a faith-based recovery group. "And I'm satisfied they are doing the right thing for her, helping her detox from the painkillers and things."
The "Georgia Rule" actress's trip to rehab capped a weekend in which she wrecked her car and was cited for driving under the influence. Police said they also discovered a substance thought to be cocaine.
Her father, who said he embraced being a Christian after serving time for DUI and assault, said he wanted to make sure Lindsay receives religious counseling.
"And I learned they use the 12-step program, which includes a lot of lessons based on God's teachings," he said. "First she needs to get clean, then she needs to let God into her life."