Spicer's resignation came just after Trump's appointment of Anthony Scaramucci as White House communications director on Friday, Axios reported, citing unnamed sources. Scaramucci was set to meet with Trump about the role Friday morning. The New York Times reported that Spicer strongly disagreed with Scaramucci's appointment.
A White House official told the Wall Street Journal Spicer briefed Trump's communications team about his departure Friday morning, before Chief of Staff Reince Priebus introduced Scaramucci to the group.
Scaramucci, a Republican donor and former Wall Street hedge fund owner, will replace Mike Dubke, who resigned in May.
Trump left the position open and has frequently complained to friends about the performance of the White House press operation, Axios reported.
Since Dubke left, Spicer has served as press secretary and filled the role of communications director. Another source told NBC News earlier Friday that Scaramucci's arrival should be seen as a strengthening of the White House staff and not a demotion for Spicer.
Scaramucci, formerly of SkyBridge Capital, works at the Export-Import Bank. He supported Trump in the 2016 presidential campaign after first supporting candidates Scott Walker and Jeb Bush. He appears on Fox News frequently as a defender of the president.
There appears to be turnover in Trump's legal team, as well.
Marc Kasowitz, Trump's personal attorney, will recede in his role, according to multiple sources. Kasowitz has been Trump's lead attorney in the Russia investigation. Attorneys John Dowd and Jay Sekulow will take over the lead in the probe, CNN reported.
Mark Corallo, the president's legal team spokesman who's been in the job for two months, is stepping aside Friday.
The staff shake-up comes as Trump's lawyers work to confine special counsel Robert Mueller's investigation of Russia's involvement in the 2016 presidential campaign. Politico reported that Corallo has grown frustrated with his role and is a supporter of Mueller's.
Friday's news also follows reports that the president is taking issue with the possibility that Mueller might examine his family's private finances.
In an interview with The New York Times on Wednesday, Trump said such an inquiry would constitute a "violation." The Washington Post reported Friday that Trump has inquired about his pardon authority -- including, perhaps, his ability to pardon himself.