"Archbishop Emeritus Desmond Tutu has checked into a Cape Town hospital for the treatment of a persistent infection and to undergo tests to discover the underlying cause," the foundation said in a statement.
He spent the morning in his office before checking into hospital. "He was in good spirits and full of praise for the care he receives."
Non-surgical treatment is expected to take five days," said the foundation.
The foundation declined to disclose the nature of the infection or which hospital he was admitted to, saying it wanted to ensure the family's privacy.
In December 2011, Tutu underwent an elective surgical procedure.
At the time, the Desmond Tutu Peace Centre declined to disclose the nature of the operation but said there was no cause for serious concern for the popular cleric who battled prostate cancer in the late 1990s.
Parties send good wishes
Political parties wished Tutu a speedy recovery.
"We wish him a speedy recovery and trust that he will soon resume his noble duties in the transformative socio-economic agenda of our country," ANC spokespeson Jackson Mthembu said.
Meanwhile, Democratic Alliance (DA) spokesperson Mmusi Maimane said the party was "saddened" by the news.
"The DA is saddened by news this evening that Desmond Tutu has been hospitalised for a recurring infection. We wish him a speedy recovery," he said in a statement.
"The Archbishop, his friends and family will be in the thoughts and prayers of a great many people around the world tonight."
Templeton Prize recipent
Tutu celebrated his 81st birthday in October.
He was recently awarded the $1.7-million Templeton Prize for his lifelong dedication to fostering "love and forgiveness".
The Nobel peace laureate was presented with the award at a ceremony in London on March 21.
The Templeton Prize, one of the world's largest annual awards, is given each year to a living person who has made "an exceptional contribution to affirming life's spiritual dimension".
Last year's winner was the Dalai Lama, Tibet's spiritual leader, who gave the money to charity.
Tutu thanked "all the wonderful people who accepted me as their leader at home" for the prize, which is administered by the US-based Templeton Foundation.
"When you are in a crowd and you stand out from the crowd it's usually because you are being carried on the shoulders of others," he said. – Sapa