The environmental lawyer will replace the retiring Senator Peter Whish-Wilson, who announced his departure from politics last October.
Ms Bleyer, who resides in Stanley on Tasmania's northwest coast, is a former president of Lawyers for Forests, chair of Environment Tasmania, and an Australia Institute spokesperson for native forests.
The 50-year-old is a veteran anti-forestry campaigner, bringing a legal action to stop a pulp mill being built in Tasmania's north, a pet project of the former state Labor government.
"I look forward to achieving outcomes for Tasmanians in the Senate, including ending native forest logging and providing safe and secure housing to those struggling without it," she said.
Ms Bleyer is likely to take her seat in Canberra in August, when Senator Whish-Wilson is expected to depart the role he has held since 2012.
Senator Whish-Wilson held a number of portfolios during his tenure but is best known recently for berating Prime Minister Anthony Albanese after the 2025 budget.
Australia's constitution dictates that retiring senators are replaced by a member of their own party, on appointment from their state or territory parliament.
By convention, it is over to the party to decide the candidate, with the Greens opening the vacancy for nominations from members and then a grassroots vote.
Ms Bleyer, with 42 per cent of the vote, beat out three other candidates: Alistair Allan, Tabatha Badger and Scott Jordan.
Ms Badger, a sitting state MP, congratulated Ms Bleyer on the win.
"Today's result is a good one for Tasmania; we have a fantastic new senator, and I remain completely committed to continuing to serve the people of Lyons through my role in the Tasmanian parliament," she said in a statement.
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