Mr Spicer stepped down because he was unhappy with US President Donald Trump's appointment of a new communications director, the New York Times reported.
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.
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.
