At the Nashville Bridgestone Arena on Dec. 19, Brooks came out on stage to help Timberlake sing "Friends in Low Places," the country star's hit from 1990.
Both artists were excited to sing together, and the crowd went wild as seen in the Instagram video shared by both below.
Brooks captioned it, "I saw an ENTERTAINER tonight! @justintimberlake #Justinrcredible," while Timberlake said, "Whoa. Whoa. Whoa. So... Yes. This happened."
Timberlake, 33, has been on his fifth concert tour called the "20/20 Experience World Tour," and just like him, Brooks is selling out shows.
The 52-year-old came out of retirement after 17 years and is on the road performing with his wife Trisha Yearwood.