32-year-old Dontrell Wise will serve a mandatory life sentence for selling deadly drugs last fall.
Wise distributed fentanyl that caused the fatal overdose of a 28-year-old Cheektowaga woman last November.
He was convicted by a federal jury Thursday.
Prosecutors said Wise also distributed heroin and cocaine.
This is the first conviction of its kind in the Western District according to U.S. Attorney James P. Kennedy.
Wise is connected to the Black Soprano gang in Buffalo, according to the FBI.
Cheektowaga Police, Buffalo Police, the FBI, and the DEA assisted federal prosecutors in the case.
Kennedy credited Cheektowaga Police especially, who he said treated the overdose scene like a crime scene, which allowed investigators to gather important evidence.
There were 251 fatal overdoses in Erie County in 2017.