Tuesday's sole sitting day is the first since Labor's sweeping state election win last month and has featured a mix of pomp and procedure.
A crowd gathered for a short welcome to country ceremony in Queen's Hall before members, including more than 40 newcomers, moved into their respective chambers to be sworn in.
Bendigo West MP Maree Edwards was re-elected speaker, while Labor veteran Shaun Leane was appointed president of the upper house unopposed after being dumped from cabinet.
After a smoking ceremony on the front steps, Ms Dessau formally declared the new-look parliament open in a speech outlining the government's plans for the next four years.
"I trust that you will work together and serve the people of Victoria with integrity and conviction," she told the packed upper house, including Premier Daniel Andrews and new Opposition Leader John Pesutto.
Normal proceedings are set to resume after her speech, with question time scheduled for both houses.
It will be Mr Pesutto's first crack at probing the Andrews government after Labor claimed a third successive election victory, extending its lower house majority to 56 seats.
One Nation Senator Pauline Hanson, who was at Victorian parliament to witness the swearing in of her party's new state MP Rikkie-Lee Tyrrell, said the Liberals failed at the ballot box after "drifting to the left".
"You've got enough lefties in the state. Let's get back to the conservative side of politics," she told reporters.
She referred to former Liberal leader Matthew Guy, who has resigned his post and moved to the backbench after leading the coalition to another election drubbing, as "Guy Matthews".
"There you are. That's how big an impression he made on me," Ms Hanson said when corrected on his name.
Mr Andrews said his newly re-elected government planned to introduce legislation on Tuesday but it would not involve signature election policies.
The Greens, whose party room has grown from four to eight, also intend to hit the ground running by introducing a bill to raise the age of criminal responsibility in Victoria from 10 to 14.
"With a progressive crossbench now in the upper house, we have a real opportunity to get on with these urgent reforms," state party leader Samantha Ratnam said.
A raft of overdue annual reports will be tabled by parliament on Tuesday afternoon, with the premier defending the lateness of their release.
"There is a shortage of auditors across the public sector right across our nation," Mr Andrews said.
"They would have been tabled earlier but they simply weren't ready."
Victorian parliament will return in earnest in early February.
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