The Albert Einstein Hospital said Pele, 74, was receiving renal support treatment, which helps kidneys to filter waste products from the blood, after he had an operation to remove kidney stones earlier this month.
A series of tweets in English from the former player's account aimed to calm concerns over his health. One read: "Want to let you know I am doing fine."
Pele's manager, Paul Kemsley, said in a statement: "He is expected to make a quick and full recovery from a minor infection caused by his recent successful surgery."
Earlier on Thursday, Pele taken into a "special care" unit in a Sao Paulo hospital after his health worsened, three days after being admitted with a urinary infection, the hospital confirmed.
"Edson Arantes do Nascimento (Pele) remains in hospital. To receive the best care he was transferred in order to be monitored in a special care unit," read a statement released by the Albert Einstein hospital in Sao Paulo.
Pele underwent surgery for kidney stones on November 13 before being released two days later.
After confirming that he had been taken in on Monday, the hospital had said that Pele remained in hospital with tests showing the presence of a urinary infection.
Two years ago, on November 15, 2012, he underwent a hip operation in the same hospital.
Pele, nicknamed O Rei (The King), was born in a humble home in the city of Tres Coracoes, but is considered by many as the greatest footballer in history with his exploits for Brazil and a career which saw him score 1,281 goals in 1,363 games.
He scored 77 goals in 91 games for his country and won his first World Cup aged just 17, scoring twice in the 1958 final win over hosts Sweden.
Image: Pele
Photograph: Neilson Barnard/Getty Images
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