The seat of Bass, southeast of Melbourne, was added to Labor's tally on Friday night.
The incumbent Jordan Crugnale declared victory over Liberal candidate Aaron Brown after a tight count which she recently led by 211 votes.
"To be re-elected for another term is beyond amazing, humbling and am streaming with tears of gratitude," Ms Crugnale wrote on Facebook.
Minister for Equality, Water and Regional Development Harriet Shing paid tribute to Ms Crugnale's success on social media.
"She just made history by being re-elected to the seat of Bass; the 56th member of a returned Andrews Labor government," Ms Shing said.
Labor won 56 out of 88 seats, the coalition secured 31 and the Greens claimed four.
The party won 55 seats in the so-called "Danslide" election of 2018.
An election for the Liberal-held regional seat of Narracan will be held at a later date after the death of Nationals candidate Shaun Gilchrist.
Despite his political fate being unclear the Liberal candidate for Narracan, Wayne Farnham, on Thursday attended the partyroom meeting where comeback MP John Pesutto was elected leader.
Mr Pesutto, 52, defeated Berwick MP Brad Battin to succeed Matthew Guy as state Liberal leader in a reported vote of 17 to 16.
The Traralgon-born former lawyer said he would work constructively with Premier Daniel Andrews, but his first priority was to hold the government to account.
With women accounting for 10 of the 33 partyroom attendees, Mr Pesutto said he was open to exploring quotas for female candidates to boost female representation.
Mr Pesutto narrowly reclaimed his seat of Hawthorn in Melbourne's inner east after losing it to retired principal John Kennedy on live TV at the 2018 state election.
The former shadow attorney-general faces a tough task to revive the party's fortunes before the 2026 election after securing 29 per cent of the primary vote in November's poll, its worst result in decades.
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