Critics have slated the Burmese leader for not speaking out against the violent persecution of Rohingya Muslims.
In an open letter that he posted on Facebook to his fellow Nobel prize winner, the 85-year-old South African archbishop said,
"I am now elderly, decrepit and formally retired, but breaking my vow to remain silent on public affairs out of profound sadness".
There have even been calls for her Nobel peace prize to be revoked, however, the overseeing organisation that this cannot be done.
Archbishop Tutu has now added his voice to many others who have called on Aung San Suu Kyi to do more to protect Myanmar's persecuted Muslim minority.
The United Nations now estimates that well over a quarter of a million refugees have crossed over into Bangladesh.
A spokeswoman for the UN high commissioner for refugees, Vivian Tan, told Agence France-Presse,
"The numbers are so alarming. It really means we have to step up our response and that the situation in Myanmar has to be addressed urgently."
Archbishop Tutu ended his letter by saying,
"As we witness the unfolding horror we pray for you to be courageous and resilient again. We pray for you to speak out for justice, human rights and the unity of your people. We pray for you to intervene in the escalating crisis and guide your people back towards the path of righteousness.
"God bless you."