A voice sounding distinctively like the 54-year-old actor is heard telling Grigorieva that she "deserved" to be hit after she chastised him for allegedly punching her in the face and breaking two of her teeth.
"What kind of a man is that?" she is heard saying in the recording, posted on celebrity website RadarOnline.com (Warning: It contains strong language). "Hitting a woman when she's holding a child in her hands? Breaking her teeth twice in the face! What kind of man is that?"
"Oh, you're all angry now!" Gibson responds. "You know what, you ... (expletive deleted) deserved it!"
Gibson goes even further by threatening to kill her.
"I'll put you in a ... (expletive deleted) rose garden," he said. "You understand that? 'Cause I'm capable of it."
Grigorieva has accused Gibson of domestic violence. The Los Angeles County Sheriff's Department which is investigating has now subpoenaed the audio tapes.
"The tapes will certainly be part of the L.A. County Sheriff's Department domestic violence allegation investigation that we opened a week ago Monday," said Los Angeles County Sheriff's Department spokesman Steve Whitmore.
The Sheriff's department said that once its investigation is complete, the case will be handed over to the district attorney's office.
On the latest tape Gibson berates Grigorieva for allegedly leaving him when he told her his career is over.
His latest film "The Beaver," is expected to be out later this year, but there is no official release date. The film is directed by Jodi Foster.
Gibson and Grigorieva have been involved in a nasty custody dispute over their infant daughter - the subject of a confidential court case.
Just last week, a recording posted by RadarOnline.com included segments it said was Gibson telling Grigorieva that she was dressing too provocatively and that it would be her fault if she were raped. He used the N-word at one point.
"In a way this is a textbook for an education class on domestic violence," said Patti Giggans, executive director of Peace Over Violence. "If people ever had any doubts about the verbal abuse part of the cycle of violence, this is it."
The Academy Award-winner has not publicly discussed the breakup with the 40-year-old singer. The former couple first revealed their relationship shortly after Gibson's wife, Robyn, filed for divorce last April. The divorce is pending.
In 2006, Gibson came under fire for a racially charged tirade when he admitted to making anti-Semitic remarks during a drunken driving arrest. He issued an apology at the time, and appealed to the Jewish community to help him recover from his alcohol addiction.
The Associated Press contributed to this report.