Lawrence Summers, a former treasury secretary during Bill Clinton's presidency, was named director of the National Economic Council and Christina Romer, an economist at the University of California at Berkeley, was named head of the White House Council of Economic Advisers.
Obama also named Melody Barnes, a former policy adviser to his election campaign, to serve as director of the Domestic Policy Council, which co-ordinates policy-making on domestic issues.
Al Jazeera's Rob Reynolds in Chicago said the announcement of the appointments was part of a confidence-building exercise aimed at reassuring Wall Street and the wider US public that his team will hit the ground running to try turning around the economic situation.
Financial markets had fallen during Obama's announcement as traders were dismayed that the president-elect did not specify the size of the stimulus package, but later rallied strongly.
The markets also appeared to welcome the bailout of Citigroup.
The US treasury department announced that it was investing $20bn in Citigroup on Sunday, as one of a series of actions to help the bank, which has lost billions of dollars amid the US economic downturn.
The government also said it would guarantee against losses of about $306bn in loans and securities held by the bank.