The woman, who has not been identified, arrived in Sydney from Los Angeles and did not have a permit for the firearm, the Australian Border Force (ABF) said.
She could face up to 10 years in jail.
Photos released by the ABF showed an airport scan of the woman's luggage, revealing the firearm inside her bag. A second photo showed the handgun after the bag was opened.
In a statement, an ABF official said that sophisticated detection technology had helped stop a dangerous weapon from entering the country.
"Time and time again, we have seen just how good ABF officers are at targeting and stopping illegal, and highly dangerous, goods from crossing Australia's border," ABF Commander Justin Bathurst said.
Officials said the 28-year-old woman was charged and appeared before the Downing Centre Local Court on Monday, where she received bail.
She could also face the cancellation of her visa and removal from Australia, pending the outcome of the court proceedings.
Airline passengers on domestic flights in the US can travel with firearms in a checked bag when they are unloaded and locked in a hard-sided case. Travellers must also tell airline representatives that they intend to travel with the weapon during check-in.
But in 2022, record number of firearms was confiscated from US airport passengers. A total of 6,301 guns were taken at checkpoints as of mid-December, the transportation Security Administration (TSA) said.
By contrast, Australia has some of the most comprehensive firearm laws in the world. They were enacted after 35 people were killed in 1996 by a gunman in Tasmania.
In the wake of the attack, all automatic and semi-automatic weapons were outlawed, and some 600,000 weapons were surrendered as part of a mandatory government buyback scheme.