Brown, in his decision, noted the barbaric nature of the murders Davis took part in.
The governor said Davis' continuing attempts to portray himself as a "passive bystander" in the murders also made him unsuitable for parole.
Davis had bragged about murdering and dismembering one of the victims, then evaded capture for more than a year in the desert with other cult members, the governor noted.
"These are not the actions of a distraught and reluctant participant," Brown said in his decision.
For the third time, Davis, 71, had been recommended for release from a life sentence for crimes committed in 1969. Brown reversed his parole grant in 2012, pressing Davis to release more details of the Manson cult's crimes.
In a 2012 hearing, Davis also admitted participating in the group's August 1969 attack on Donald “Shorty” Shea, a stuntman and hand at the ranch where the Manson cult was living and whom
"I've known people that said we don't want you here," he said in March, "so I said if there's any sort of objection, I would be glad to go to San Francisco."