The first lady announced the move, which takes effect immediately, in a statement Tuesday.
"I am excited to welcome Stephanie back to the team in this new role," Melanie Trump said. "She has been a mainstay and true leader in the administration from even before day one, and I know she will excel as chief of staff."
Grisham left the first lady's office last July to take over as President Donald Trump's top press officer, replacing Sarah Huckabee Sanders. Grisham, who never staged an on-camera press briefing in her nine months in the role, was Trump's third press secretary after Sanders and Sean Spicer.
Grisham's departure is one of several moves new White House chief of staff Mark Meadows is making. Multiple news outlets reported that Trump campaign spokeswoman Kayleigh McEnany is expected to replace Grisham as press secretary.
"I continue to be honored to serve both the president and first lady in the administration," Grisham said in a statement. "My replacements will be announced in the coming days and I will stay in the West Wing to help with a smooth transition for as long as needed."
Trump has complained at times about public relations issues that have reflected poorly on the White House, particularly during the coronavirus pandemic.
"We've done a poor job on press relationships, and I guess, I don't know who to blame for that," Trump said recently. "Maybe I can blame ourselves for that. ... But I think we've done a great job. I think we've done a poor job in terms of press relationship."