Biden, 78, presented his picks for secretary of state, national security adviser, homeland security secretary, intelligence chief, UN ambassador and climate change envoy, AFP reported.
Biden said that after he is inaugurated on January 20 and President Donald Trump leaves the White House, the United States will be "ready to confront our adversaries and not reject our allies" in a jab at Trump's go-it-alone "America First" policies.
"It is a team that reflects the fact that America is back," Biden said as the six men and women stood behind him wearing face masks.
Biden's remarks came after Trump suffered further setbacks in his efforts to overturn the results of the election with unsubstantiated claims of fraud.
Pennsylvania and Nevada certified the November 3 election results Tuesday, a day after the state of Michigan did so, a move which triggered the General Services Administration (GSA) to launch the transition process.
As more members of his Republican Party came out demanding an end to the impasse, Trump signed off on the GSA move, effectively admitting defeat.
But the president on Tuesday tweeted a picture of himself with the caption "I concede NOTHING!!!!!"
The GSA determination gives Biden access to classified information and will allow his aides to coordinate with officials on addressing the worsening coronavirus pandemic.
"We're already working out meeting with the COVID team in the White House... The outreach has been sincere," Biden told NBC in his first TV interview since winning the presidency.
Biden said that in his first 100 days in office he would tackle the COVID crisis, scrap Trump policies "damaging" the environment and push legislation offering millions of undocumented residents a route to citizenship.
The slate that Biden unveiled included veterans of the Barack Obama administration and signaled a return to traditional US diplomacy and multilateralism.
Biden said that "America's going to reassert its role in the world and be a coalition builder," but he denied it would be like a third term of Obama – whom he served as vice president.
"We face a totally different world," the president-elect said. "President Trump has changed the landscape. It's become America First, which meant America alone."
Antony Blinken, Biden's choice for secretary of state, said the United States cannot solve global problems on its own.
"We need to be working with other countries," the former State Department official said.
However, outgoing Secretary of State Mike Pompeo denounced Biden's call for greater international cooperation, saying that Trump had been focused on "real results" and "the reality on the ground."
Former secretary of state John Kerry, who Biden chose as his special envoy on climate change, confirmed that the United States will rejoin the Paris climate accord which, under Trump, it formally withdrew from earlier this month.
Cuban-born Alejandro Mayorkas was named to head the Department of Homeland Security, whose policing of tough immigration restrictions under Trump was a frequent source of controversy.
Avril Haines was nominated to be the director of national intelligence, the first woman to hold the post, while Jake Sullivan was named national security advisor.
Former Federal Reserve chairwoman Janet Yellen is expected to be named Treasury secretary, the first woman to hold the job.