The board recommended parole for Davis based on his positive adjustment, lack of recent disciplinary problems and successful completion of educational and self-help programs, KTLA-TV, Los Angeles, reported.
Gov. Jerry Brown has 120 days to reverse, modify, affirm or decline to review the decision, the TV station said.
Davis was given two life sentences for the 1969 killings of musician Gary Hinman and stuntman Donald "Shorty" Shea but was not involved in the widely publicized murders of actress Sharon Tate and six others in Los Angeles.
He became an ordained minister and obtained master's degrees in philosophy and religion during his 40-year stay in prison.
The board recommended parole for Davis in 2010, but Gov. Arnold Schwarzenegger reversed the decision, citing the "especially heinous" nature of the killings and Davis' attempts to evade responsibility for his actions.