Bulger showed no emotion as he learned he was convicted in a string of 11 killings and other gangland crimes, many of them committed while he was said to be an FBI informant. The jury found that prosecutors did not prove Bulger killed or ordered the killings of eight other people.
The 83-year-old was charged primarily with racketeering, a catchall offense that listed 33 criminal acts, including 19 murders that he allegedly helped orchestrate or carried out himself during the 1970s and '80s while he led the Winter Hill Gang. The racketeering charge also included acts of extortion, money-laundering and drug dealing. He pleaded not guilty to charges.
Bulger was one of the nation's most-wanted fugitives after fleeing Boston in 1994, but he was captured in Santa Monica in May 2011.
During the two-month trial, prosecution witnesses portrayed Bulger as a hands-on crime boss who killed some of the gang's targets himself and orchestrated other killings. The jury deliberated for 32 hours over five days before reaching the verdict.
Bulger did not testify during the trial.
"I feel that I've been choked off from having an opportunity to give an adequate defense," he told a judge at the end of his trial. "My thing is, as far as I'm concerned, I didn't get a fair trial, and this is a sham, and do what youse want with me. That's it. That's my final word."
Bulger's defense lawyer Jay Carney said Bulger was "pleased by the outcome. It was important to him that the government corruption be exposed."
According to Carney, Bulger plans to appeal his verdict.
Bulger could get life in prison when he is sentenced on Nov. 13. But given his age, even a modest term could amount to a life sentence.
ABC News and The Associated Press contributed to this report.