The news comes a day after Hicks, 29, spent hours testifying before the House Intelligence Committee in its investigation into Russian interference in the 2016 election. Hicks told lawmakers she sometimes had to tell white lies in her job, but did not lie about matters related to the probe, according to The New York Times.
She considered stepping down for months, according to the Times, which first reported the news.
The communications director, who previously worked in public relations for Ivanka Trump's clothing brand, signed on early to President Donald Trump's small presidential campaign. She eventually rose to one of the top positions in the White House.
CNBC reports Trump issued a statement praising Hicks. He said she came to him about "pursuing other opportunities."
Hicks, who rarely spoke publicly, had the difficult task of controlling the message from an often chaotic White House. For much of Trump's presidential campaign she led its response to press inquiries, and the president reportedly had great trust in her.
|Hicks, Porter (Daily Mail photo)|
Hicks had been under scrutiny since at least early February for her role in the White House's handling of the scandal surrounding Rob Porter, the former staff secretary who was accused of physically and emotionally abusing two of his ex-wives.
Hicks had been romantically involved with Porter was said to have helped write a White House statement defending him amid the allegations.
"What happened yesterday just put the nail in the coffin for her," said April Ryan, a White House correspondent and CNN contributor. Citing her own sources in the West Wing, Ryan said Hicks had given a tentative resignation after the Porter incident. She suggested that what happened on Wednesday "was a forced resignation."