Former lower house MP Deborah O'Neill has been elected by Labor to fill the Senate vacancy caused by the retirement of former minister Bob Carr.
Labor leader Bill Shorten says the party will be stronger with Ms O'Neill in the parliament.
"I'm pleased she's back to continue her hard work and to help hold the coalition to account over their plans to cut services and assistance families rely on," he said in a statement.
She was elected after the NSW ALP's administrative committee met on Wednesday to vote on who would take the upper house spot.
Ms O'Neill fended off two other nominees, small business operator Michelle Miran and farmer Vivien Thomson.
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She must be formally endorsed by a joint sitting of both houses of the NSW parliament before taking her seat on November 12.
Mr Carr announced last week he was leaving the Senate after 18 months, following Labor losing government on September 7.
He was marshalled into government by former Labor prime minister Julia Gillard as foreign minister and continued that role under her successor Kevin Rudd.
