The Victorian Liberals met on Wednesday night to preselect a candidate for the November 18 poll to replace former premier Daniel Andrews as Mulgrave MP.
Courtney Mann emerged as the winner, beating out three other preselection nominees.
Mr Mann ran as the Liberal candidate for Mulgrave at the 2010 state election and is a senior policy adviser in Mr Pesutto's office.
He also has previous experience as an adviser in the Baillieu/Napthine Victorian coalition governments.
Mr Pesutto said Mr Mann had deep roots in the electorate, having grown up in Mulgrave and lived there for 25 years.
"He is highly respected across the party and, if elected, would provide a strong voice for the people of Mulgrave in the Victorian parliament," he said in a statement.
Labor holds the seat on a healthy 10.2 per cent two-party-preferred margin but it could be reduced following the retirement of Mr Andrews last month after more than 20 years as the local member.
Dandenong mayor Eden Foster, who grew up within Mulgrave's suburbs of Noble Park and Springvale, has been locked in as Labor's pick to succeed him.
Ms Foster's fellow councillor Rhonda Garad was preselected as the Victorian Greens' candidate.
Ian Cook, who is suing the Victorian health department after he was ordered to shut his catering business over the listeriosis-linked death of an elderly woman, confirmed he would recontest the seat after collecting the second most first-preference votes last year.
Nominations for the Mulgrave by-election close next week.
It will be the second Victorian state by-election this year after the Liberals retained Warrandyte in Melbourne's northeast following the retirement of veteran MP Ryan Smith, in a poll Labor did not contest.
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