Luis Cruz was the third of four defendants to be sentenced in connection with the drugs linked to the death of Williams, who overdosed in his Brooklyn penthouse apartment in September 2021.
Williams died four hours after authorities said he bought the heroin from another member of the crew.
A federal judge in Manhattan imposed the prison time on Cruz, who pleaded guilty in April to a reduced charge of narcotics conspiracy.
Cruz's lawyer, Deborah Colson, said in an email that Cruz "accepted responsibility and provided a genuine, heartfelt apology." She declined further comment.
In a letter to the judge, Cruz, who had been an electrician, said he was addicted to drugs and was selling them to support his habit and pay his bills.
"It was a terrible mistake in judgment," he wrote.
Federal prosecutors, however, said Cruz and the drug crew kept selling the fentanyl-laced heroin even after Williams' death. A search of Cruz's apartment found more than 500 small bags of the deadly heroin and drug paraphernalia, authorities said.
Williams, who was 54, was known for portraying Omar Little, the rogue robber of drug dealers, in HBO's The Wire, which ran from 2002 to 2008.
In addition to his work on the critically acclaimed drama, Williams also starred in films and other TV series such as Boardwalk Empire.
The drug crew member who sold the drugs to Williams, Irvin Cartagena, was sentenced to 10 years in prison in August.
Another crew member was hande more than two years in prison, and the fourth person awaits sentencing.
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