At a "special conference" on Friday, Burnham, who earned the moniker "King of the North" for his determination as mayor of Greater Manchester to defend the region's interests, said he was ready for power and would work to offer hope to people in "forgotten places everywhere".
"We are united and we put the power that comes from that unity at the service of people and places who have been waiting too long for politics to let them hope again," he told a room full of Labour MPs and party officials on Friday.
"And that's what we're going to do, everybody, we're going to give them hope back."
He also paid tribute to Keir Starmer, the man he will replace as British prime minister on Monday, when the party will be eager to find out his cabinet team and learn more about his approach to government.
Despite his offer of hope to places that feel 'left behind', there is still much to know about how Burnham will govern.
He has given one speech since returning to parliament last month after winning a seat in Makerfield, the start of a four-week process to remove Starmer, whose unpopularity across Britain turned his MPs against him, and take his place as prime minister.
In it, he sketched out some of his domestic agenda, saying he wanted to oversee the "biggest rebalancing of power" from London to Britain's regions - something he believes will reduce inequality and the anger felt by "left-behind communities" who have increasingly flocked to Reform.
That message of having a plan to thwart the rise of Reform won over Labour MPs, who feared they would lose their parliamentary seats to veteran Brexit campaigner Nigel Farage's populist party at the next national election, due by 2029.
Reform has topped opinion polls for months.
Some of that sheen has been tarnished in recent weeks by Farage's acceptance of funds from wealthy donors, perhaps giving Burnham an opening to revive Labour's fortunes.
Yet he does not have much time.
With a general election no more than three years away, Burnham will need to start implementing some of his pledges, many of which are based on long-term thinking, as quickly as possible.
Nigel Wilcock, executive director at the Institute of Economic Development, an independent body representing economic development professionals, said Burnham had spent years making the case for a different approach to economic growth:
"The challenge is turning that vision into a reality."
