The victims, mostly women, were trampled to death as about 1,500 spectators scrambled out the stadium to escape the riot that broke out just before midnight Sunday, said Lt. Col. Gede Sumerta Jaya, police spokesman in Papua province.
Kota Lama Sport Stadium in the town of Nabire had only two working exits.
Points awarded by a panel of judges decided the championship match for the Bupati Cup, or Regent Cup. The losing boxer's supporters threw chairs at the judges and the winner's supporters responded by throwing bottles and broken chairs, panicking people in the stadium, Jaya said.
He said 12 of the dead were women, and more than 40 other spectators were injured and hospitalized.
Police and soldiers were deployed to stop the fighting.
Nabire, about 3,200 kilometers (2,000 miles) east of Jakarta, is located on Cendrawasih Bay on the north coast of Papua.