Archaeologists found it in August inside a small underground tomb near Iznik, a town known for the Council of Nicaea in 325.
The tomb is thought to date to the 3rd century, when Christians still faced persecution in the Roman Empire.
The fresco shows a young, clean-shaven Jesus in a toga carrying a goat across his shoulders. Researchers say examples of the Good Shepherd in Anatolia are uncommon and that this one is the best preserved.
Walls around the image include birds, plants and portraits of noble figures with attendants.
The excavation also uncovered the remains of five people, including an infant.
