Kate was snapped while taking a stroll with her son in the grounds of Government House at Yarralumla in Canberra, apparently by the paparazzi.
The images show George being carried on his mother's shoulders, being pushed in a buggy and sitting on Kate's lap as the pair play together.
The Duke and Duchess were also photographed without their knowledge walking hand in hand along the foreshore of Lake Burley Griffin at Government House, casually dressed in shirts, jumpers and jeans.
The pictures taken on a rest day during their tour down under are likely to be seen as an intrusion into the couple's privacy by aides.
Tomorrow, William and Kate will travel to Uluru, one of Australia's most iconic sites. The Cambridges will tour the popular tourist attraction - also know as Ayers Rock - that is a sacred site for the area's Aboriginal people.
The visit will be only their second night away from their eight-month-old son during their 19-day tour of Australia and New Zealand.
The couple took their baby to Sydney's Taronga Zoo, where George met a bilby - a rabbit-like marsupial - that was named after him.