Labor state secretary Stuart Benson said Mr O'Byrne was elected with 74 per cent of the total votes submitted.

"I congratulate David O'Byrne on his election and welcome this new era for the Tasmanian Labor Party," Mr Benson said.

"This ballot allowed the vast majority of Party members the opportunity to vote in an historic democratic process.

IN OTHER NEWS:

More than 1200 party members took part in the vote.

Delegates at Labor's 2018 conference changed the way new leaders could be selected if there was a contest, as there was between Mr O'Byrne and Braddon's Shane Broad.

Mr Benson said the ballot meant party members were able to engage directly with both leadership candidates.

"This was about allowing rank-and-file party members to have a frank and open choice over the future of our party," he said.

After the announcement, Mr O'Byrne released a statement on his Facebook page.

He described the leadership as an enormous honor and responsibility.

"I have spent my entire working life fighting to make a positive difference in lives of others and I will continue that work in this most important of roles," Mr O'Byrne said.

"It's important because of the many people that rely on Labor to be at our best, that we not only deliver good government but that we provide opportunities for all and assistance for those in need and deliver a more just Tasmania.

"Labor at our best builds a stronger future and leaves nobody behind."

He thanked former leader Rebecca White for her support and fellow ballot contender Shane Broad for "ensuring that there is healthy debate and cooperative competition inside our party."

Mr O'Byrne was first elected to Parliament in 2010 and was soon appointed with a heavy ministerial workload which included the economic development, infrastructure and workplace relations portfolios.

He only served one term, however, with Labor failing to retain its two seats in Franklin.

Mr O'Byrne was then re-elected in 2018.

He started his career in the union movement with the Health and Community Services Union and much later served as the national secretary of United Voice.

Mr O'Byrne has also served as state president of Tasmanian Labor.

Dr Broad was first elected to Parliament on a recount in 2017 following the resignation of former Labor leader Bryan Green.

He was elected in his own right in the 2018 and 2021 state election campaigns.

Greens leader Cassy O'Connor earlier in the day predicted Mr O'Byrne would take the leadership due to union backing.

"It'll then be up to David to outline a vision for Labor because that's what has been sorely lacking ever since they went into opposition," she said.

Deputy Premier Jeremy Rockliff earlier in the week said Labor had a lot of work to do to rebuild itself after the May state election.

"We've got a Labor Party that is extremely divided, dysfunctional, and really controlled by union bosses," he said.

"Irrespective of their leader, they have a lot of work to do quite clearly."