The state’s Department of Health and Human Services confirmed on Sunday the woman landed in Melbourne from Iran.
The Victorian woman travelled from Tehran via Kuala Lumpur and Bali, arriving in Australia around 6 a.m. on Friday.
She started feeling unwell while travelling to Melbourne, and authorities are following-up with fellow plane travellers.
The health department said the woman travelled by private car directly home, which eliminates the risk of further public exposure sites.
She was admitted to hospital on Saturday and put in isolation, then confirmed positive for the COVID-19 virus on Sunday.
Another person who was in contact with the woman will be tested for the virus and has been forced to self-isolate at home for 14 days.
This new case comes as the federal government defends its decision to ban foreign visitors entering Australia from Iran to prevent the spread of the coronavirus, rather than South Korea which has a much higher level of cases.
Home Affairs Minister Peter Dutton on Sunday said that of the 106 deaths that have been reported outside of China, 43 have been in Iran.
A 63-year-old Gold Coast beautician who returned to Australia from Iran on Monday, has also been diagnosed with the virus.
Seven previously confirmed cases in Victoria have recovered and are no longer in isolation.
The eighth, case a man in his 70s who was aboard the Diamond Princess cruise ship quarantined in Japan, was on Sunday transferred to Melbourne from quarantine near Darwin.