The visit to the cemetery – which is the traditional resting place of US military members – is an inaugural tradition.
Barack and Michelle Obama and Bill Clinton and Hillary Rodham Clinton also joined the newly inaugurated president for the ceremony.
The wreath laying was one of Mr Biden’s first official actions at president.
The Tomb of the Unknown Solider is a monument dedicated to American military members who died without their remains being identified. It is among the most iconic structures in Arlington National Cemetery.
Wreath laying ceremonies at the tomb are common for heads of state.
Mr Biden was sworn in as president at noon and delivered a speech calling for unity in the country and an end to the “uncivil war” between liberals and conservatives, who became increasingly polarised under former president Donald Trump’s administration.
“This is our historic moment of crisis and challenge,” Mr Biden said. “And unity is the path forward. And we must meet this moment as the United States of America. If we do that, I guarantee you we will not fail.”
The inauguration was extremely scaled back compared with past ceremonies, largely due to the potential for a mass audience event to spread the coronavirus, as well as due to the potential threat from Trump supporters in the wake of the US Capitol riots.
More than 25,000 National Guard troops were deployed to Washington DC to secure the nation’s capital after the insurrection at the Capitol that left five people dead.
Mr Trump departed Washington DC earlier in the day. He gave a final farewell address to a small gathering of supporters before he and his wife Melania Trump flew to Florida.
Mr Trump plans to take up permanent residence in his Florida golf resort, Mar-a-Lago.