The Associated Press called the victory for DeSantis at 11:35 p.m. on Tuesday.
DeSantis, justifiably, thumped his chest in victory.
In the end, Trump's candidate won.
The other big race in the state is the U.S. Senate contest between incumbent Democrat Bill Nelson and Republican Gov. Rick Scott.
Meanwhile, DeSantis, who's stepped down from US Congress to run in this race, told supporters in Orlando he has a "proven record of being the leader Florida needs". During a Fox News appearance the day after the primaries, DeSantis said "the last thing we need to do is to monkey this up by trying to embrace a socialist agenda with huge tax increases and bankrupting the state", in reference to his new opponent, a 39-year-old black man.
It's unclear why it took so long to correct the error, but the network has come under fire during the President Donald Trump presidency for moving further and further to the left.
He advocated for stricter immigration laws, repealing former President Barack Obama's Affordable Care Act, and has said that he would have vetoed the legislation that provided stricter gun control measures after 17 people were killed during a shooting rampage at Florida's Marjory Stoneman Douglas High School.
Republicans put forth a candidate hand-picked by President Donald Trump. More than 973,000 voters with no party affiliation have also voted.
Accordingly, Trump and race occupied the mind of almost every voter. I believe the Dems could have won this race with a better candidate than Andrew Gillum.
DeSantis on Tuesday night pledged to keep Florida's taxes low and protect its environment by standing up for clean water, stopping red tide and restoring the Everglades.
Rep. Jeanette Nunez, a Miami Republican who is running for lieutenant governor with DeSantis, slammed Gillum for Tallahassee's crime rate, which is above the state average based on population. "To me, it's all about results", DeSantis added. His candidacy was seen as a boost for the more vulnerable Democratic Sen. Gillum has repeatedly maintained that he is not the target of the wide-ranging FBI investigation into Tallahassee's city hall and that he got the tickets from his brother. The Mayor had vehemently denied being a "target". But DeSantis made it stick, even though Gillum has yet to be subpoenaed by the Federal Bureau of Investigation, and the agency hasn't commented on his vulnerability as a leader. If he wins the general election, he'd be the first Black Governor in the state's history. Phillis and Jeffrey voted for Andrew Gillum.
"In less than one week, Americans will go to the polls in one of the most important elections of their lives", Trump said at the rally, before qualifying that this election was "not as important as 2016".
Going into Election Day, the math favored Democrats: Nearly 23,000 more registered Democrats than Republicans had voted statewide, out of 5.2 million ballots cast early. "At least in this election".
It was Trump's support, including a July endorsement rally in Tampa, that helped propel DeSantis past a better-funded and more widely known opponent, Agriculture Commissioner Adam Putnam, in the August 28 Republican primary.
Gillum doled out less than $7 million ahead of the August 28 primary and won against the other four Democratic hopefuls - all of which had outspent him.
Mr Gillum has conceded the race.
The latest polls show Gillum in the lead by an average of four points, according to an analysis by Real Clear Politics.
In this case, that appears to be right.
"We could not be prouder of the way that we ran this race". We could not be more thankful for the support that was shown by each and every one of you. "Will you join us?", DeSantis wrote on Twitter.
Gillum said he called DeSantis and congratulated him. "But I want you to know that, in spite of our congratulating him on his victory this evening, nothing that we believe in is compromised", Gillum said.
If Gillum wins, he will be the first Democratic governor elected by Floridians in 20 years.