The money comes from the Federal Aviation Administration to improve terminal safety and support two infrastructure projects at the facility.
According to a release, the city plans to modernize the airport’s taxiway and replace critical parts of the terminal's central utility plant.
The $20.3 million grant is among the largest amount given to an agency in Florida.
"We set a goal five years ago to increase our receipt of annual grant awards as part of our focus on strong fiscal stewardship practices, and I could not be prouder of the results the team has achieved," City Manager Reese Goad said.
Monday's announcement comes as JetBlue is preparing to leave the city next month, less than a year after hosting its first in-state flight from Tallahassee the Fort Lauderdale.
But last Wednesday, Silver Airways announced the addition of a daily flight route from Tampa to Tallahassee beginning Oct. 7.