The purpose of this paper is to describe the early introduction protocols in a hand-reared Gorilla infant (Gorilla gorilla) that was introduced to biological parents at Kyoto City Zoo. The introduction process was initiated when the infant was one year old. In Dec. 21, 2011, an infant gorilla was born at Kyoto City Zoo. The infant is the first one who has captive-born parents, and the fourth generation of gorillas in Japan. The mother successfully held the infant, but could not give her milk enough to feed the infant. The baby showed dehydration and weakened. For the purpose of saving its life, we separated the infant from the mother and began to rear it. To avoid harmful influence of hand-rearing, we planned to reintroduce the hand-reared infant to its parents on the basis of successful cases in European and American zoos. We separated the processes of reintroduction into five steps, each of which had no time-limit, but totaled one, or one and half years. We started to show the infant to the parents when the infant was two months old. In the beginning, each of the parents showed a gentle attitude, and then started to directly contact with their infant. Habituation with the physical environment and the parents was going smoothly under careful observation. We returned the infant to its mother successfully at 10.5 months of age. Then, in its 11.5 months of age, we reintroduced the mother and the infant to the adult male (i.e., the father of the infant). Finally, the parents and the infant live together peacefully now. We thought of the processes of reintroduction and found one of the most important factors was that separation was attributed by not giving up nursing, but insufficiency of milk. Another factor may be that separation period was short enough to induce a sense of responsibility as a mother.