That is a large audience for a daytime event, though it is short of the 30.6 million who tuned in to President Donald Trump's inauguration in January.
Nielsen's estimates include people watching on 10 US broadcast and cable television networks, but not those who streamed the congressional hearing on computers or mobile phones. Broadcasters interrupted regular programming to air nearly three hours of live coverage of Comey's remarks about his dealings with Trump before the president fired him in May.
The tally was impressive for an event that aired during the work day, when typically only events like state funerals and royal weddings draw mass viewing, said Jeffrey Jones, director of journalism's Peabody Awards and a professor at the University of Georgia. Jones was traveling and saw crowds gathered around TVs in Atlanta's airport to watch the hearing.
"Politics is quite often about theater and drama, and this was a classic showdown," he said. "People wanted to see it for themselves."
The television ratings do not include the many people who watched the highly anticipated hearing during at bars and restaurants or online through TV network apps or on social media sites.
Alphabet Inc's YouTube reported nearly 800,000 peak concurrent viewers across streams from 20 news outlets. Twitter Inc. said the average minute audience for its livestream of Bloomberg's coverage was 129,000 viewers.
During his appearance, Comey told the Senate Intelligence Committee that he believed Trump dismissed him to try to undermine a Federal Bureau of Investigation probe into possible collusion between Trump's 2016 presidential campaign team and Russia.
Trump on Friday said Comey's testimony showed "no obstruction."
(Reporting by Lisa Richwine; Editing by Leslie Adler)
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)