Gestational length of the koala is 34 to 36 days.  It has been observed in captivity, however, that the gestational length is at least 50 days (Gifford et al.).  This distinction is important for researchers to understand because it can dictate management methods.  More research still needs to be done to determine the large difference in gestational length between wild and captive animals. 

The mother will then give birth.  After birth, the young joey will immediately climb into its mother's pouch and firmly attach itself to one of its mother's teats.  The young stays attached to its mother's teat for the entire time spent in the pouch.  At this point it can be referred to as a "pouch young."  The young koala is hairless and bears little resemblance to the adult koala.  After about thirteen weeks, the koala will start to resemble the adult.  At about 22 weeks the joey will peek its head out of the pouch.  Once out of the pouch the joey will start feeding on pap, which is a runny derivative of the mother's feces.  Upon first emerging from the pouch, the joey will attach to its mother's belly until it is old enough to climb onto its mother's back.  The now named "back young" will stay with its mother until it is about a year old.  By this time, the mother usually gives birth to a new cub, forcing the year old joey to leave.  The young koala will stay in the same tree as its mother, but will feed on its own and no longer be allowed on its mother's back.  In the next year or so the koala will leave its mother and find its own home range.

Females usually give birth to their first young at around 18 months of age.  The young rarely survive when the mothers are this young.  The first successful pregnancy occurs around 2 years of age.  Males can start to reproduce at 2 years of age, but are usually prevented from doing so by the older male koalas.  The 2 year old male will be much smaller in size than the dominant male, so it is easy for the dominant male to prevent the young males from reproducing.