Last week, ESPN reported the 155-pound matchup had been targeted to headline the event, which will take place at Wells Fargo Center and air on the network.
Gaethje (19-2) is coming off a riveting first-round knockout against James Vick this past August. The Denver native was originally supposed to fight Al Iaquinta on that date, but Iaquinta withdrew due to a contract dispute. Gaethje has said he still wants to fight Iaquinta at some point but will face Barboza next.
A former WSOF champion, Gaethje is 2-2 since coming to the UFC in 2017. He is known as one of the most entertaining fighters in the sport.
Barboza (20-6), of Rio de Janeiro, knocked out Daniel Hooker in his most recent appearance, at UFC Fight Night on Dec. 15. He has lost two of his past three contests, but both losses came against top competition: Khabib Nurmagomedov and Kevin Lee.