Hundreds gathered with the Nobel peace prize winner at St Mary's Cathedral in central Johannesburg.
The Anglican Archbishop Emeritus, 84, was dean at St Mary's when he was appointed bishop of Lesotho 40 years ago.
He later became the first black archbishop of Cape Town where he was an outspoken opponent of South Africa's apartheid regime, which enforced a harsh system of racial discrimination.
He was awarded the Nobel peace prize in 1984 for his campaigning.
Since the end of apartheid in 1994, Tutu has campaigned for human rights, to fight HIV and Aids, racism, sexism, homophobia and transphobia.
He has been in and out of hospital for some time and battled cancer, raising fears about his health.
Earlier this year his daughter Mpho Tutu had to leave the priesthood because she married her same sex partner.
