Mike Duggan was holding initial staff meetings at City Hall on Wednesday after the morning ceremony, continuing the work he has done on Detroit's behalf since voters elected him in November.
With outgoing Mayor Dave Bing at his side, Duggan praised his predecessor, calling him one of his heroes.
"I'm going to continue to build on what he started, and I just want to say thank you," Duggan said during a brief ceremony punctuated by humor and informality.
The former Detroit Medical Center chief has attended a meeting of new mayors hosted by the White House, put together his own administration and lobbied with emergency manager Kevyn Orr for a greater role in the city's immediate turnaround.
"He's been engaged on issues and has been preparing to hit the ground running," former Detroit Councilwoman Sheila Cockrel said of Duggan.
So far, mayoral-type celebrations have been muted, something Cockrel said is noteworthy.
"We're broke. There is no money. Streetlights are still not on. Cops do not come on time," said Cockrel, who is founder of a government relations advocacy firm. "When you're in the middle of a bankruptcy, how much celebrating should you be doing? It's about the city. The most important thing for all of us now is getting the city's organization and finances in operating order."
With snow falling on the city Wednesday, Duggan was asked by reporters whether he was going to observe the work of city road crews.
"When you get elected to office, you don't automatically have all the answers," Duggan said, drawing laughs.
Under Michigan's emergency manager law, Orr has control over Detroit's finances. He filed the city's bankruptcy petition in July. On Dec. 3, federal Judge Steven Rhodes made Detroit the largest U.S. city to enter bankruptcy.
"We have a division of responsibilities that I respect," Duggan said. "I'm going to do the best job I can."
"I expect that we're going to have a relationship based on the agreement we've reached," he added. "I'm going to disagree on some things."
Orr, who didn't attend the ceremony, was appointed by Gov. Rick Snyder in March. Orr has said that Detroit has at least $18 billion in debt. He's negotiating with the city's many creditors and is expected to release a plan of adjustment for Detroit's restructuring early this month.
Bing, Duggan's predecessor who didn't seek re-election, had complained of his diminished role since Orr was hired.
Duggan announced Dec. 19 that he and Orr agreed to share some of the duties in running the city, with the bulk of financial responsibilities still under the emergency manager's control.
"You're going to see a lot of activity, even in the next two weeks," Duggan said then.
Under the deal with Orr, Duggan takes on blight removal, public lighting and the Fire Department, and will control financial matters relating to the day-to-day function of city government.
"I'm hopeful that with the tools that he was given ... we will see an improvement in service delivery," said Gabe LeLand, who was elected in November to his first term on the Detroit City Council.
At Wednesday's ceremony, Duggan said that he would "be dealing with things like getting the buses running and the snow plowed and those kind of day-to-day things that people in Detroit deserve."
The nine council members already have taken their official oaths of office. Duggan will officiate at a ceremonial swearing-in for the council on Tuesday, said LeLand.
The powers of the council also are restricted under the state's emergency manager law.
Detroit councils and mayors have frequently been at odds, dating back decades. Duggan said Wednesday that he has met personally with the new members but acknowledged the possibility of future challenges.
"I have a very good relationship with all of the nine members. ... It always stays like that doesn't it?" Duggan asked Bing, drawing a wave of laughter.