FEMA Administrator Pete Gaynor sent Newsom a letter Oct. 14 that said "it has been determined that the damage from this event was not of such severity and magnitude as to be beyond the capabilities of the state, affected local governments, and voluntary agencies."
A FEMA spokesperson also told Fox News earlier in the day Friday that the request had been denied because "damage assessments FEMA conducted" determined that the federal government's assistance wasn't necessary.
That assessment changed at some point on Friday.
“Just got off the phone with President Trump who has approved our Major Disaster Declaration request," Newsom said Friday afternoon in a statement. "Grateful for his quick response."
A spokesman for California's Office of Emergency Services told Fox News that it "appears the federal government has reversed course."
Newsom originally sent a letter to the White House on Sept. 28 requesting the Major Disaster Declaration and funds to help recover from six early September wildfires: the Valley Fire, El Dorado Fire, Creek Fire, Oak Fire, Bobcat Fire and Slater Fire.
"Thus far, these fires have scorched more than 1,887,932 acres, destroyed 3,368 structures, including nearly 1,000 homes, and damaged an additional 232 structures," Newsom wrote in the letter. "Tragically, the fires have also claimed the lives of at least three people."
A declaration by the president makes people in impacted counties eligible for support such as crisis counseling, housing, unemployment assistance and legal services. It also allows the federal government to give assistance to state, local and tribal governments to fund the emergency response.
California previously secured a disaster declaration from the White House in August to support relief efforts for wildfires in the northern part of the state.
President Trump has threatened to cut off the federal government's assistance in fighting California's wildfires, tweeting in 2019 that Newsom "has done a terrible job of forest management."
More recently, Trump said during the first presidential debate last month that "we have to do better management of our forests."
California has frequently sparred with the president in court, suing his administration dozens of times over everything from the census to health care.
More than 8,500 blazes have scorched 6,400 square miles in California's historically devastating 2020 wildfire season.
The season isn't over yet though, as nearly 9,000 firefighters continue to fight 21 fires.
The Associated Press contributed to this report.