The incident was captured on camera by a television crew from Nightline whom Hayek allowed accompany her on the goodwill trip in September.
The 42-year-old actress, who was nursing her own daughter Valentina at the time, offered to help when the baby's mother stopped producing milk.
"The baby was perfectly healthy, but the mother didn't have milk. He was very hungry. I was weaning Valentina, but I still had a lot of milk that I was pumping, so I breast-fed the baby. You should have seen his eyes. When he felt the nourishment, he immediately stopped crying," Hayek said.