Amanda Bynes has been transferred to UCLA Medical Centre at the request of her mother.
Amanda's mother - who was recently granted temporary conservatorship over the former child star - is said to have wanted her daughter moved, gossip website TMZ.com reported.
Sources said Amanda would have been transferred earlier but a bed wasn't available. She was seen hiding under a blanket and wearing a bright blue wig as she left the Hillmont Psychiatric Centre.
The 27-year-old actress is being treated for mental illness and is reportedly being tested for schizophrenia.
Amanda, the former star of Nickelodeon show All That and her own variety series, has been in a psychiatric hospital since last month. Authorities placed her in hospital after she started a small fire in the driveway of a house in her hometown of Thousand Oaks, California.
In May, Amanda was arrested in New York for allegedly throwing a marijuana bong out of the window of her 36th-floor Manhattan apartment.
Last year, Amanda was charged in Los Angeles with driving on a suspended licence. The licence had been suspended after she was charged with driving under the influence and misdemeanour hit-and-run.