The surprise change in defence lawyers unfolded at a court hearing where Nick Reiner, 32, had been expected to enter a not-guilty plea in one of the most shocking celebrity homicide cases in Los Angeles history.
Instead, the arraignment was postponed for the second time in three weeks.
The Los Angeles County Superior Court judge rescheduled the proceeding for February 23.
Alan Jackson, a former prosecutor turned criminal defence lawyer whose clients have included a number of one-time show-business luminaries, including disgraced film producer Harvey Weinstein, announced in court on Wednesday that he was withdrawing from the case but gave no immediate reason.
The judge assigned a public defender to take Jackson's place for the time being.
Nick Reiner is charged with two counts of first-degree murder in the fatal knife attack on his parents - actor-director Rob Reiner, 78, and photographer-producer Michele Reiner, 70.
Their bodies were found on the afternoon of December 14 inside their west Los Angeles mansion.
Prosecutors have said the pair were killed early that morning.
Authorities have disclosed few details about the circumstances of the crime and offered no explanation for what may have precipitated the killings.
Autopsies found both victims died from "multiple sharp force injuries".
If convicted as charged, Nick Reiner would face life in prison without the possibility of parole, or the death penalty.
The son was widely reported to have quarrelled with his parents while the three were attending a holiday party hosted by comedian Conan O'Brien the night before the couple were found slain.
Nick Reiner, who has publicly acknowledged a years-long struggle with drug addiction and periods of homelessness, had lived in a guest house on his parents' property.
He was arrested near a downtown Los Angeles park several hours after their bodies were discovered.
Rob Reiner was known for a prolific show-business career that ranged from co-starring in the 1970s hit television comedy All in the Family to directing the beloved 1989 film When Harry Met Sally... and was also a prominent Democratic Party activist and donor.
