Late Thursday, Facebook announced Zuckerberg had also made a visit to the White House -- issuing a statement similar to the one earlier in the day, but adding the visit with the president.
"Mark is in Washington, D.C., meeting with policymakers to hear their concerns and talk about future internet regulation," the company said in a statement. "He also had a good, constructive meeting with President Trump at the White House today."
The spokesman also said Zuckerberg will “definitely” be on the Hill for another day of meetings Friday, but declined to name which lawmakers are scheduled to meet with him.
The tech executive's visit to the capital comes just a day after chiefs from his own company, Facebook, as well as Google and Twitter faced a Senate committee to testify about "digital responsibility" in the spread of extremism online.
Earlier this week Facebook also announced changes to its policies for combating hate and extremism on its namesake platform and Instagram, including updating its definition of terrorist organizations and revamping detection efforts.
As part of those changes, Facebook said it is working with law enforcement in the U.S. and U.K. to obtain their footage from firearms training programs to train their machine learning systems about how to spot first-person footage of violent events, such as the mass shooting in Christchurch, New Zealand, that left 50 dead and was livestreamed online.
It is also the first time Zuckerberg has returned to Capitol Hill since he was called to testify before Congress over the company's involvement in the Cambridge Analytica data privacy scandal.
ABC News' Mary Kathryn Burke and John Parkinson contributed to this report.