Mercado del Toro died at his home in the town of Isabela, about 70 miles west of San Juan, of natural causes, his grandniece, Dolores Martinez, told The Associated Press.
"He died like a little angel," Martinez said.
Mercado del Toro had been having difficulty breathing recently but was conscious and alert shortly before his death, Martinez said outside the family home.
At his death, he was with a great-grandnephew and a caretaker, she said.
Mercado Del Toro, who was born in Puerto Rico when it was still a Spanish colony, was drafted into the U.S. Army in 1918 but did not serve in combat because World War I ended while he was still in training. Later, he worked in the island's sugar cane fields.
He was married three times but never had children.
In Isabela, Mercado del Toro was a local celebrity after he was recognized by Guinness World Records for his longevity.
"We're all crying, but we knew this day would come," said town spokeswoman Rosa Luciano.
Mercado Del Toro became the oldest known person in the world last month when 116-year-old Elizabeth "Lizzie" Bolden died in December in a nursing home in Tennessee.
A 114-year-old Connecticut woman, Emma Faust Tillman, is now believed to be the oldest living person. Tillman, listed by Guinness World Records' Web site as a former servant for famed actress Katharine Hepburn, She was born Nov. 22, 1892.