The American eased past Italy's Lucia Bronzetti 6-1, 7-5 to book her place in the main draw as she returns from a foot injury that kept her off tour for most of last year.
Stephens, the 2017 US Open champion and French Open finalist a year later, lost to top-ranked Aryna Sabalenka in Melbourne in 2025 before being sidelined by injury.
The 32-year-old played no competitive tennis between February and September.
"Obviously, the last round of qualies is not easy and I haven't been there in a long time, so a little bit stressful but really happy to get the win and get through," Stephens, a former world number three, said.
"I think I was the only Grand Slam champion to be in qualies, which was interesting, I was like, 'Oh God, a lot of pressure', but I was just like it's an opportunity to go and play and try and figure it out."
Emerging Turkish star Zeynep Sonmez also advanced, downing Anastasia Gasanova 6-3, 6-2.
The 23-year-old made headlines at Wimbledon last year, becoming the first player from Turkey to reach the third round at a Grand Slam in the Open era.
"After Wimbledon, of course Grand Slams feel more special right now, and I love to play in Australia," she said.
"I'm happy that I qualified, and looking forward to playing my first match in the main draw."
