The 37-year-old performed an acoustic set to warm up the crowd in Louisiana before Garth's main show, but he made a surprise return to the spotlight during the veteran musician's performance to team up on a track Lee had written for Brooks a decade ago.
As Garth introduced More Than A Memory, he recalled hearing the tune for the first time during his career hiatus.
"Lee Brice had this song called More Than A Memory that he had written," Brooks told the crowd. "And there's a thing in Nashville - this has never happened to you, it happens to me all the time - but you'll hear the demo of the song, and you realise you'll never be able to sing it that good (sic)."
Then, delivering a big compliment to Lee, he continued, "So, I'm gonna have my stab at it and then I'm gonna let the master take over."
The pair then launched into the 2007 track, trading verses for the special performance, reports CMT.com.
Taking to Twitter after the gig, Brice wrote, "One of my favorite nights on a stage ever."
It's not the first time Lee has been invited to sing with Brooks - they played the same tune together for the first time in January, 2015, when they duetted for fans in Boston, Massachusetts.