Being able to breastfeed in the chamber follows new rules introduced last year to create a more a "family friendly" parliament.
Greens' senator Larissa Waters returned to the upper house Senate for the first time Tuesday since giving birth to her second child, and brought her in for a feed during a vote.
"So proud that my daughter Alia is the first baby to be breastfed in the federal Parliament! We need more #women & parents in Parli," she wrote on Twitter.
Being able to breastfeed in the chamber follows new rules introduced last year to create a more a "family friendly" parliament in the wake of what has been described as a "baby boom" among politicians.
Under previous rules, children were technically banned.
"In 2003 Kirstie Marshall, a Victorian MP, was ejected from state parliament for breastfeeding her 11-day old baby girl," Waters added.
"Sometimes it’s difficult not to get disheartened by the sexism women still face in the workplace. But sometimes it pays to look back and see how far we have come."
Breastfeeding in public has become a hot topic in many countries, and female lawmakers have been criticised for taking their babies to parliamentary sessions.
Last year, a politician in Iceland spoke in parliament while breastfeeding her baby daughter, and infants are allowed in the European and Spanish parliaments.
Labor frontbencher Katy Gallagher said the moment deserved to be acknowledged.
"Women have been doing it in parliaments around the world... It is great to see it is able to occur now in the Senate," she told Sky News.
"Women are going to continue to have babies and if they want to do their job and be at work and look after their baby... the reality is we are going to have to accommodate that."
Waters has changed her Facebook profile to an image of herself breastfeeding in parliament, attracting dozens of mostly positive comments.
"Thank you for sharing this beautiful picture and helping to normalize breastfeeding in our society!" one user wrote.
Another added: "yessss, you are such a legend. thanks for being such a strong, groundbreaking woman."