The animals – one adult, four cubs and all – were seen at Sydney’s Taronga Zoo around 6:30 on Wednesday (22:30 GMT Tuesday).
One cub had to calmly be put into lockdown, but the rest of the lions were safe within minutes, according to a spokesperson. There were no injuries.
There is no explanation for the escape.
Simon Duffy, executive director of the Zoo, called it “significant” and said that an investigation would be conducted.
He said that the lions entered a small area adjacent to their exhibit, about 100m from the hotel where they were staying. The main zoo was still closed at that time.
He said, “The lions never exited that area [adjacent] or Taronga Zoo.”
Duffy explained that the fence was six feet high and was used to protect the area. A perimeter fence was also installed around the entire zoo.
The CCTV footage had revealed that a keeper raised an alarm within 10 minutes after the escape.
According to Mr Duffy staff responded quickly to move all those on the site into safe areas. Four of the four lions “calmly made it back” to their enclosure.
Mr Duffy said that the lion exhibit would remain closed until further inspections were done to ensure that it is “100% secure”.
Escapes of animals at Australian Zoos are very rare.
2009 saw a lioness escape from Mogo Zoo south of Sydney and was forced to be killed due to the threat it posed.