The actress has been admitted to the Promises centre in Malibu, where Britney Spears spent her recent rehab spell. Her decision follows her arrest last weekend in Los Angeles, for drink and drugs charges.
A friend of Lohan reveals the decision was actively made by the star, adding: "She finally realises it's the right thing to do. She is going willingly."
The spell in rehab could put Lohan's latest film in the balance - Poor Things is currently being filmed in Santa Monica, and it was originally thought that she would travel daily to the film shoot.
However, TMZ reports that the actress will not be allowed to leave the centre for around a month, leaving the Shirley MacLaine film hanging on a decision.