Bulger, 83, was found responsible for 11 of the 19 murder allegations against him; the jury gave no finding in one death. Bulger was also convicted on racketeering, money laundering, narcotics, extortion and conspiracy charges, The Boston Globe reported.
As he was leaving the courtroom after his conviction, Bulger pointed at his family and gave them a thumbs-up. A member of the gallery shouted back "Rat-a-tat, Whitey." Several family members of those killed by Bulger's gang cried as the jury's findings for each individual victim were read aloud in the courtroom, the Globe said.
Bulger, a former boss of South Boston's notorious Winter Hill Gang, ran roughshod in the city's underworld from the 1970s until the 1990s.
A federal jury deliberated the case for five days after hearing weeks of testimony, much of which laid bare the inner workings of an FBI field office where agents and players in the city's mob scene colluded, shared information and exchanged money for favors.
Bulger himself, though he has denied the claims, was accused of working with corrupt FBI agents, including his handler, John Connolly, who turned a blind eye toward Winter Hill gang crimes in exchange for information about other criminal elements -- and passed Bulger tips to help him avoid arrest. Several of his former confidants and top lieutenants testified against him during the trial after cutting deals with prosecutors, saying they were shocked when they found out Bulger was working with the FBI.
Bulger, after being charged in the indictment, fled Boston in 1995 and evaded law enforcement until his capture in Santa Monica, Calif., in 2011.
U.S. Judge Denise Casper thanked the jury of four women and eight men for their work, saying she thought they took the case "very seriously." She said they were free to speak with members of the media if they choose.
Bulger faces likely life in prison at sentencing in November.