Labor's Jordan Crugnale has retained her seat of Bass, meaning the party has surpassed its 2018 "Danslide" in the lower house.
She beat Liberal challenger Aaron Brown for the electorate south-east of Melbourne, which takes in Phillip Island and Wonthaggi.
The result means Labor won 56 seats in the lower house, one up from the last state election.
Ms Crugnale thanked her supporters on Facebook following the news of her win.
"It was always going to be close with or without the redistribution and I have never once taken anything for granted," she said.
"It's been a privilege and honour to work for and with our community and together we have achieved so much.
"To be re-elected for another term is beyond amazing, humbling and am streaming with tears of gratitude."
The election for the seat of Narracan was delayed after the death of the Nationals candidate.
In the lower house, Labor holds 56 seats, the Coalition 27 and the Greens 4.
The upper house count has not been finalised, but the current composition is Labor on 15 seats, the Coalition on 14, Legalise Cannabis on 3 and the Greens on 2.
On one seat each are the Liberal Democrats, Animal Justice Party, Shooters Fishers and Farmers, Transport Matters, Democratic Labour Party and One Nation.
