The Victorian Liberals have claimed victory in one of two Victorian by-elections after the Greens conceded defeat.

Rachel Westaway edged out Greens candidate Angelica Di Camillo in the inner-Melbourne state seat of Prahran on Sunday afternoon, marking the first time it has changed hands in more than a decade.

Greens leader Ellen Sandell blamed the loss on preferences and the by-election's timing.

"Obviously, it's not the result we would have liked, but with the unofficial Labor candidate sending their preferences to the Liberals, those Labor preferences have handed the seat to the Liberals this time," she said.

"The Greens' high primary vote is something to be proud of and especially in a by-election held during the uni summer holidays.

"Low turnout shows a lot of young people, and traditional Greens voters, wouldn't have even known an election was on."

Labor did not run a candidate in Prahran.

Opposition leader Brad Battin said the victory was due to voters becoming despondent with the Greens and Labor "destroying their lives".

"They're sick of the crime here in Prahran. They're sick of the cost of living, their rents going up. They're sick of the congestion," he told reporters.

"They want Prahran, once again, to be the Chapel Street that they used to remember.

"They want to be able to park on the street and not have to worry whether the next morning they wake up, if their car is going to be there or not."

The result remained too close to call in a second by-election in Werribee, triggered by the resignation of former treasurer Tim Pallas.

With AAP.