Nicknamed “Scholzomat” for his robotic, jargon-filled speeches bulging with policy details, the 59-year-old is considered a safe choice to preserve predecessor Wolfgang Schäuble's fiscally conservative legacy in Berlin and Brussels — despite hailing from the centre-left Social Democrats (SPD).
Scholz's promotion marks the first time since 2009 that the SPD is back in control of the powerful finance portfolio. But with Chancellor Angela Merkel's conservatives still smarting from the concession made to seal their coalition deal, Scholz has been careful not to rub salt in the wound.
“The SPD stands for solid finances,” he told Der Spiegel weekly, confirming he would stick to Schäuble's cherished “black zero” goal of a balanced budget.
But sceptics are watching closely, aware that Scholz is not afraid to loosen the purse strings.
To ensure the architecturally stunning but much-delayed Elbphilharmonie concert hall would be spared further time overruns, Scholz agreed to pay the construction firm an extra €200 million in taxpayer money, bringing the total bill to 800 million — over 10 times the original budget.
But the controversial project has since won over even the most ardent critics and cemented Hamburg's status as a cultural hotspot.
As mayor of Germany's second-largest city since 2011, Scholz also oversaw the introduction of free daycare for children and a boom in affordable housing.
For Scholz, whose motto is “I can only distribute what I have”, the spending was justified by the city-state's healthy finances.
Andrea Nahles, the SPD's designated next leader, praised Scholz's fiscal rigour and vision when she formally announced his ministerial appointment on Friday.
Scholz had led the wealthy river port “with a keen eye on finances, with budgetary discipline on the one hand, and future-oriented investments in education, research and infrastructure on the other,” she said.
The biggest wobble of Scholz's career so far came during last year's riot-hit G20 summit in Hamburg when anti-capitalist protesters torched cars, smashed windows and clashed with police in scenes that shocked Germany.
Critics castigated Scholz for underestimating the security challenges of the high-profile event, but he resisted pressure to resign.
As he packs his bags for Berlin, Scholz is gearing up to wear many different hats.
As well as serving as interim SPD chief and taking on the finance brief, he is set to be vice-chancellor in Merkel's new cabinet — making him one of Germany's most influential politicians.
But observers suspect the man often described as meticulous, confident and fiercely ambitious has set his sights even higher, and hopes to become chancellor one day.
“No one can accuse the Hamburg mayor of lacking in perseverance,” Die Zeit weekly commented about his slow but steady rise.
Born in the northern city Osnabrück, Scholz joined the SPD as a teenager.
He flirted with its more leftwing ideals but soon came to prefer a more centrist course.
After training as a lawyer specialized in employment, Scholz was elected to the national parliament in 1998. He married fellow SPD politician Britta Ernst that same year.
It was during his 2002-2004 stint as the SPD's general secretary that he earned the “robot” moniker for his dry yet tireless defence of unpopular labour reforms then-chancellor Gerhard Schröder was pushing through.
As labour minister in Merkel's first coalition government from 2007 to 2009, Scholz helped avert mass lay-offs during the financial crisis by convincing firms to cut workers' hours with the state topping up their salaries.
He also proved he could work well with Merkel.
The SPD's deputy leader for almost a decade, he played a key role in weeks of tortuous coalition negotiations with her conservative bloc earlier this year.
The power pact they hammered out promises to maintain Schäuble's policy of not running up new debts, but also backs deeper eurozone integration and greater German contributions to the EU budget post-Brexit.
European peers hoping for a break from hardliner Schäuble's austerity mantra for troubled eurozone economies were heartened by Scholz's recent comment that he didn't want to “dictate” policies to other countries.
But business weekly WirtschaftsWoche cautioned against expecting radical changes.
“He won't abandon German insistence on sound finances and clear fiscal rules in Brussels any more than Schäuble did,” it wrote.