Johnson, 35, a professional boxer for 16 years, had been in critical condition since being put in a medically induced coma after undergoing surgery for bleeding on the brain.
Johnson, from Atlantic City, was hit hard throughout the fight against Mexico's Jesus Chavez at the MGM Grand before the bout was stopped 38 seconds into the 11th round. Chavez opened the round by landing a steady stream of blows - all to the head - that kept a dazed Johnson pinned to the ropes. He collapsed later in his dressing-room.
"All of my prayers are with Leavander Johnson and his family," said Chavez, who visited him in hospital. "He was a true warrior with a tremendous heart, and every day I will think of him. He will never be forgotten."
Chavez has vowed to donate a portion of each purse he makes while IBF lightweight champion to a fund set up for Johnson's four children.
Johnson won the title in June, beating Stefano Zoff in Italy.Reuse content