LOS ANGELES—A Los Angeles man accused of killing his wife and her parents and then stuffing their dismembered body parts into trash bags pleaded not guilty Friday to murder.

Samuel Bond Haskell IV, 35, entered pleas to three counts of murder with special circumstances of committing multiple murders. If convicted, he could face life in prison without the possibility of parole.

An email seeking comment from his attorney, Joseph Weimortz, wasn’t immediately returned.

Mr. Haskell is the son of Emmy-winning producer Sam Haskell, a former executive at the powerful William Morris talent agency.

The younger Haskell lived in the Tarzana neighborhood of the San Fernando Valley with his wife, their three young children, and her parents.

He was arrested in November on suspicion of killing Mei Haskell, 37; her mother, Yanxiang Wang, 64; and stepfather, Gaoshan Li, 72.

Prosecutors say that on Nov. 7, Mr. Haskell hired four day laborers to remove bags from his property. The workers said they were paid $500 and told that they were hauling away rocks, although the bags felt soggy and soft.

“One of the laborers opened one of the bags and allegedly observed human body parts,” the Los Angeles County District Attorney’s Office said in a November statement.

The laborers said they drove back to Mr. Haskell’s home, left the bags on the driveway, and returned the money. They contacted police but by the time officers arrived, the bags were gone, according to a KNBC-TV Channel 4 report.

The next day a homeless man found a duffel bag containing a human torso in a Tarzana dumpster. Mr. Haskell was arrested a short time later.

The Los Angeles County coroner determined the torso belonged to Mei Haskell. The remains of her parents haven’t been found.

If convicted, Mr. Haskell could be sentenced to life in prison without possibility of parole.