He was reportedly given a crash course in "public speaking, humility, and charm" by hired a team of experts, including a former special assistant to former US president George W Bush. Facebook's mission is to "help people connect".
He added that Facebook fell short in protecting the platform, noting: "That goes for fake news, foreign interference in elections and hate speech, as well as developers and data privacy".
Zuckerberg testified before the U.S. Senate Commerce, Science and Transportation Committee on Tuesday. Dick Durbin asked the Facebook founder and CEO if he would be comfortable sharing the name of the hotel he was staying at in Washington.
Zuckerberg said that Facebook allows people to decide whether and how they want their information shared. A number of the Russian ads were on Facebook. It's an arrangement to which Facebook's users agree and can sidestep, technically, but it is hardly informed consent or a real option to avoid.
Mr Zuckerberg said this was done for security purposes.
Facebook CEO Mark Zuckerberg is back on Capitol Hill.
Until now, it's been used mainly to describe financial institutions that have become so vital to our system that their collapse could take down the larger economy.
The hearing opened with members of the House of Representatives asking Mr. Zuckerberg questions during allotted four-minute segments.
The 33-year-old billionaire appeared humble throughout much of the hearing, with only a few smug smiles.
Facebook plans to reveal all the third-party apps that have authorization to access user data, the company said. Indeed, the company makes it money through advertising, but not by providing data to advertisers, but instead doing the work for them. It did note one comment that might be said to have been influenced by the social network's largesse. "So my position is not that there should be no regulation but I also think that you have to be careful about regulation you put in place".
Similarly, upon being asked if Facebook needs greater regulation, he tried to steer the debate away from a yes and no situation.
In the aftermath of the exposé in March 2018, Facebook's first reaction was to deny each emerging detail.
Facebook's chief executive has revealed that his data was among that harvested in a privacy scandal.
Zuckerberg told a lawmaker during his appearance Wednesday he believes the notices about Cambridge Analytica's possession of their information began going out Monday.
The stakes are high for both Zuckerberg and his company.
Facebook may be making itself safer or more secure, but it hasn't answered the question of whether we should continue to interact with it at all.
When some new manipulation creates an outcry, Facebook makes a show of apologizing.
"Your success story is an American success story", Rep. Greg Walden, the chairman of the committee, said in his opening remarks.