About 39.87 million watched the swearing in of Biden as president and Kamala Harris as vice president. That's up from the 27.08 million that watched Donald Trump become president in 2017. CNN led all cable networks with 9.9 million, while ABC was tops among broadcasters with 7.66 million. Biden's viewership was the most for an inauguration since Barack Obama's in 2009. ALSO: Fox News' Biden viewership 77% lower than its audience for Trump's inaugural, while MSNBC's more than quadrupled.