Nick Reiner, 32, is being held in a Los Angeles County jail on a $US4 million ($A6 million) bond, according to jail records.
Los Angeles police said their investigation "determined that the Reiners were the victims of homicide" and that their son "was responsible for their deaths."
Police said they found two bodies at the Reiners' home at 3.40pm on Sunday in the Brentwood neighbourhood of Los Angeles on Sunday.
Officials confirmed the victims were Reiner, 78, and his wife Michele, 68.
Local media reported the couple had been stabbed to death.
Outlets reported that Nick had been spotted arguing with his parents on Saturday night at a holiday party hosted by comedian Conan O'Brien.
Nick Reiner spoke openly over the years about his struggles with substance abuse and about being homeless at times when he was on the run and refusing to go into rehab.
He told People magazine in a 2016 interview that he first went into rehab for drug abuse at age 15 - and that he eventually had at least 17 stays in rehab facilities over the years.
Rob and Nick Reiner co-wrote the film Being Charlie, based on Nick's experiences with heroin addiction and homelessness.
"It was the most personal thing I've ever been involved in," Rob Reiner told podcaster Marc Maron in 2016.
Nick told People, "when I was out there, I could've died."
Tributes poured in for Bob Reiner.
"This is a devastating loss for our city and our country. Rob Reiner's contributions reverberate throughout American culture and society, and he has improved countless lives through his creative work and advocacy fighting for social and economic justice," Los Angeles mayor Karen Bass said in a statement.
Reiner's role as Meathead in Norman Lear's 1970s TV classic All in the Family, as a progressive foil to O'Connor's Archie Bunker, catapulted him to fame and won him two Emmy Awards.
Reiner went on to have a prolific Hollywood career as a director, starting with This is Spinal Tap, a 1984 mockumentary about a fictional hard rock band.
The film became a cult classic, known for its mostly improvised script, with Reiner playing the faux documentary filmmaker Marty DiBergi.
"That was the trick - to make fun of it and at the same time, honour it," Reiner told CBS this year as he promoted a sequel, Spinal Tap II: The End Continues.
Reiner directed nearly two dozen films in all, including classics such as Stand by Me, a 1986 coming-of-age drama about four boys who set out to find the body of a missing youth, and 1989's When Harry Met Sally, often cited as one of the greatest romantic comedies of all time.
That movie featured the famed line, "I'll have what she's having," delivered by the director's real-life mother, Estelle Reiner, reacting to a faked orgasm in a restaurant.
Reiner also directed the 1987 fairy-tale adventure The Princess Bride, the 1990 psychological thriller Misery and the 1992 military courtroom drama A Few Good Men.
The son of comedian Carl Reiner, Rob Reiner was married to photographer Michele Singer Reiner since 1989.
The two met while he was directing When Harry Met Sally and have three children together.
Reiner was previously married to actor-director Penny Marshall from 1971 to 1981.
He adopted her daughter, Tracy Reiner.
Carl Reiner died in 2020 at age 98 and Marshall died in 2018.
Killings are rare in the Brentwood neighbourhood.
The scene is about 1.5km from the home where OJ Simpson's wife Nicole Brown Simpson and her friend Ron Goldman were killed in 1994.
with AP
