Hicks, one of Trump's most trusted aides, served as White House communications director until resigning in February 2018 when she was appointed communications chief at Fox.
Hicks, who previously served as Trump's campaign press secretary, will be working closely with the president's son-in-law and advisor Jared Kushner and White House Political Affairs Director Brian Jack, a White House official said without disclosing the specific issues she would focus on.
When the now 31-year-old Hicks, a former Ralph Lauren model, became the White House communications director, she worked from a tiny office outside the Oval Office as a gatekeeper and sounding board for the president.
"There is no one more devoted to implementing President Trump's agenda than Hope Hicks", Kushner said in a statement. Details were still being worked out Thursday.
Hicks was also a key witness in former special counsel Robert Mueller's investigation and the Senate Intelligence Committee Russia probe.
She announced her resignation a day after she testified behind closed doors before the House Judiciary Committee last June as part of its investigation into whether the president obstructed justice.
Stephanie Grisham, the White House press secretary and current White House communications director, said that after working with Hope for nearly six years she can say "without hesitation she is one of the most talented and savvy individuals I have come across".
Hicks did not immediately respond to a request for comment.
Hicks left the White House in March 2018.
However, Hicks remained in close contact with Kushner and other top White House aides. He was ousted two yeas ago on the orders of former chief of staff John Kelly, before being reinstated by Trump two months ago.
Ex-Trump aides Sean Spicer and Reince Priebus are also being given new roles.