Mr. Hagman died at 4:20 p.m. Friday at Medical City Dallas Hospital after being diagnosed with cancer, according to the Morning News.
In a statement in 2011, he had said: "As J.R. I could get away with anything - bribery, blackmail and adultery. But I got caught by cancer."
Hagman declined to specify what kind of cancer he's contracted, but said it's "a very common and treatable form." He continued working on a new reboot of "Dallas" for TNT.
The new "Dallas" focuses on the Ewing offspring as they clash over the future of the family dynasty. The original prime-time soap opera aired on CBS from 1978 to 1991. Hagman underwent a liver transplant in the mid-1990s.
Said Hagman in 2011: "As we all know, you can't keep J.R. down!"
He was also on the 60s TV series "I Dream of Jeannie."