The 84-year-old Bulger was convicted last year in a broad racketeering case, including 11 killings and other gangland crimes in the 1970s and 80s.
The appeal is to be filed Thursday with the 1st U.S. Circuit Court of Appeals. Bulger's lawyers previously have said he believes he should have been allowed to argue that a now-deceased federal prosecutor gave him immunity.
Bulger headed Boston's Irish mob and was an FBI informant against the rival New England Mafia. His case became an embarrassment for the FBI when it was learned corrupt agents accepted bribes and protected him.
He was a fugitive for 16 years until his 2011 arrest in California.