In his initial acts as the 46th US president, he signed 15 executive orders – the first to boost the federal response to the coronavirus crisis.
Other orders reversed the Trump administration’s stance on climate change and immigration.
President Biden set to work at the Oval Office having been sworn in earlier on Wednesday at the US Capitol.
The inauguration was unlike any other due to coronavirus restrictions, with few present to witness the oaths and ceremonies.
Donald Trump – who has still not formally conceded the presidency to Mr Biden – snubbed the event in a departure from longstanding precedent.
“There is no time to waste when it comes to tackling the crises we face,” President Biden tweeted as he headed to the White House following his inauguration.
President Biden “will take action – not just to reverse the gravest damages of the Trump administration – but also to start moving our country forward,” a statement detailing his executive orders said.
On coronavirus, a series of measures will be enacted to tackle the pandemic which has claimed more than 400,000 lives in the US.
There will be a mandate to wear masks and practise social distancing on all federal government property.
A new office will be set up to co-ordinate the response to the pandemic and the US will halt the process – begun by the Trump administration – of withdrawing from the World Health Organization (WHO).