The Koala reaches sexual maturity at around 3 to 4 years, being that the females are more precocious.

The gestation time is about of 33 to 36 days. Koalas mate, or make babies, in the spring and summer. About 35 days after mating, a female gives birth to a tiny immature animal named Joey.
A Joey is only about 0.8 of an inch (2cm) long, it has no fur, and its eyes and ears are not formed. Baby koalas are born pink, bald, blind, and about the size of a jelly bean.

After emerging from the birth canal, the blind little creature clings to the fur on its mother’s stomach. As soon as it is born, the Joey knows by instinct that it must find its mother’s pouch. It must make its way across its mother’s belly to her pouch. If it fails to crawl inside the pouch, it will not survive. But the tiny baby almost always succeeds. A newborn koala must immediately crawl into its mother’s pouch. This journey is very difficult and usually takes 5 minutes. The first five minutes after birth may be the most important of its life.

The Joey cannot see or hear, and its back legs have not yet grown. It uses only its front legs to pull itself across its mother’s belly. They have an excellent sense of smell. This sense of direction helps it to climb to its mother’s pouch. It can smell milk in the pouch and find milk following the scent of the milk. As soon as the Joey crawls inside the pouch, the little Joey attaches itself to one of the mother two teats that provides it with nourishing milk.

It begins sucking on a nipple. The nipple swells inside the baby’s mouth so that the Joey cannot let go or fall off when its mother moves around. The milk it drinks give the Joey the nutrients, or nourishment, it needs to grow.

The Joey remains in the pouch for the first six to seven months of its life, feeding on its mother’s milk.