Mr Spicer stepped down because he was unhappy with President Donald Trump’s appointment of a new communications director, according to reports.
Combative Wall Street financier Anthony Scaramucci has been picked for the role that Mr Spicer partially filled.
Mr Spicer’s press briefings were a cable news hit, but he withdrew from camera in recent weeks.
He told US media that the White House “could benefit from a clean slate”.
The shake-up comes as the White House faces inquiries into alleged Russian meddling in last year’s US presidential election and whether Mr Trump’s campaign team colluded with Moscow.
The New York Times reports that 45-year-old Mr Spicer “vehemently” disagreed with the appointment of Mr Scaramucci, which he believed to be a “major mistake”.
The search for a new appointment began after Mike Dubke resigned from the communications director job in May.
Mr Spicer has been serving as both press secretary and communications director since Mr Dubke’s exit.
“It’s been an honor & a privilege to serve @POTUS @realDonaldTrump & this amazing country,” Mr Spicer tweeted.
“I will continue my service through August”.