A woman in her 30s and her four children, including a two-week-old infant, have been missing since Friday, September 27 and were last seen in Goulburn.
NSW police said 35-year-old Rochelle Watts is believed to be travelling with her children - a 15-year-old boy, a 10-year-old boy, an eight-year-old girl and a newborn girl.
The mother was last seen in Goulburn about 2.30pm on September 27.
She has been described as being of Caucasian appearance, about 165 centimetres tall, with a large build, red hair, and hazel eyes.
Police said the family's German shepherd - Elsa - was also with them.
"When concerns were raised for her welfare, officers attached to the Hume Police District were notified and commenced inquiries into her whereabouts," a police spokeswoman said.
She said police and family members had serious concerns for her welfare.
The mother is believed to frequent the Goulburn and Tirrannaville areas.
"Police are also following up a report that Rochelle may be in the Murgon area, Queensland," the spokeswoman said.
She said ACT Policing and other interstate agencies had been notified about the mother and children.
"Police are still making enquiries," she said.
Anyone with information about their whereabouts was urged to call Goulburn Police Station or Crime Stoppers on 1800 333 000.
