A "compassionate release" was requested for Atkins after a physician said she has a terminal illness and is expected to die in less than six months, said Terry Thornton, spokeswoman for the California Department of Corrections and Rehabilitation.
Atkins has spent the last 37 years behind bars after being convicted in the 1969 killings of seven people, including actress Sharon Tate. Atkins was also found guilty of killing music instructor Gary Hinman.
Officials have not said who called for Atkins' release, the Los Angeles Times reported Friday.
Sources familiar with the case say Atkins has battled brain cancer and had one of her legs amputated.
The California Institution for Women in Corona, where Atkins was held until March when she went to a medical center, has authorized her release, the newspaper said.