In his new memoir, Good Vibrations, the singer explains he hired incarcerated killer Susan Atkins to look after his children in the late 1960s.
Atkins was among those involved in a cult-led killing spree in August,1969.
And in an excerpt from his book printed in the new issue of People magazine, Love reveals his estranged wife Suzanne turned to Atkins for child minder help while she was dating his Beach Boys bandmate Dennis Wilson.
He didn't find out about the babysitter's true identity until after the Manson Family murders, when pal Terry Melcher informed him his wife and her lover once left the couple's two young children with Atkins.
"Atkins testified that she held Sharon Tate - who pleaded with the killers to spare her life and that of her unborn child - while another assailant, Charles 'Tex' Watson, stabbed her to death," Love writes. "In a theatrical flourish, Atkins used Tate's blood to write 'PIG' on the outside of the front door.
"She was convicted of participating in eight murders and was sentenced to death. And she was our babysitter."
Atkins' sentence was later commuted to life in prison. She died behind bars in 2009, aged 61.