As the royals arrived, Archbishop Tutu and his wife took turned to coo over the four-month-old, trying to teach him to wave to the cameras.
Baby Archie, the son of Britain's Prince Harry and his wife Meghan, took part his first public engagement on Wednesday.
His parents brought the four-month-old to meet Archbishop Desmond Tutu and his wife Nomalizo Leah Tutu in South Africa on Wednesday.
As the royals arrived, Tutu and his wife took turned to coo over the baby, trying to teach him to wave to the cameras.
Archie later sat with his parents as the four talked further.
The couple shared video of them carrying their son, who can be heard making an exclamation whilst in Meghan's arms.
Ahead of the visit, Tutu and his wife, Leah, said they viewed the interaction with the Duke and Duchess of Sussex as a "rare privilege and honour".
A Nobel Peace Prize laureate, Tutu, who used the pulpit to preach against the injustices of white minority rule during apartheid, has battled prostate cancer for years and has largely withdrawn from public life.
The Duke and Duchess of Sussex are on their first overseas tour since the birth of Archie, their first child, who is accompanying them on their visit.
Harry, Queen Elizabeth's grandson and sixth in line to the throne, has been visiting southern Africa for two decades for holidays and conservation work.