Santillan's passing was confirmed by the World Boxing Council. A statement read: "RIP Hugo Santillan.
"He passed away from injuries suffered during Saturday's fight which ended in a draw.
"We join Hugo's family and friends in grief, support and wish prompt resignation."
Santillan died with a 19-6-2 record, with his fatal draw coming in a fight for WBC Latino Silver lightweight title.
The 10-round fight took place at the Club Atletico San Nicolas in Buenos Aires.
The tragedy comes just days after Russian fighter Maxim Dadashev also died following injuries from the weekend.
The late Russian, 28, underwent emergency brain surgery following his 11th-round defeat in an IBF light-welterweight title eliminator in America.
Dadashev had the right side of his skull removed to ease brain swelling after suffering a subdural haematoma in Saturday's brutal clash.
The operation, performed by Neurosurgeon Mary I.H. Cobb, reportedly took several hours and the St Petersburg-born fighter was then placed in a medically induced coma.
But the super-lightweight lost the most important fight of his life and passed away because of the seriousness of his injuries.
Trainer James "Buddy" McGirt stopped the fight against Puerto Rico's Subriel Matias after the Russian missed a number of punches in the 11th round.
The stablemate of Vasiliy Lomachenko then collapsed in front of his fans before leaving the arena — having struggled to walk out of the ring.
Dadashev's wife posted an emotional message on social media as tributes poured in from the boxing world.