Shelton opened the performance solo in a simple three-piece suit and tie with guitar in hand, before Stefani -- dressed in a sheer white, fairy tale-inspired heart-adorned gown with a floral headband, a gorgeous long train and ruby and diamond earrings by Karen Suen -- joined midway through for the heartwarming love song.
"I don't wanna live without you. I don't wanna go down any other road," the couple sang, the meaning of the lyrics taking on an added layer following news of Bryant's sudden death.
When Keys cued up their duet, she called them two people who were there to celebrate their love. The 50-year-old rocker and 43-year-old country singer inspired major couple goals with their lovey-dovey duet. After they finished their performance, the couple adorably embraced, with Shelton bowing down to Stefani.
"Gwen was crying when we even just talked about singing it together at all," Shelton said. "It just seemed to fit perfectly with our story, and, musically, I think it walks the line of what I can do and what she can do. Everything just kind of aligned and came together, and it's one of those once-in-a-lifetime moments."
In addition to performing, Shelton's "God's Country" was also nominated for Best Country Solo Performance at the GRAMMYs.
The awards show comes just hours after ET confirmed that Bryant, the legendary basketball star, died in a helicopter crash in Calabasas, California. He was 41. His 13-year-old daughter, Gianna, was also on board the helicopter and died alongside her father. Keys, who was hosting the GRAMMYs, paid tribute to Bryant, Gianna and the seven other lives lost with a touching a capella performance with Boyz II Men.
Staples Center is home to the Los Angeles Lakers, where Bryant played from 1996-2016. He is survived by his wife, Vanessa, and their three other children -- Natalia, 17, Bianka, 3, and Capri, 7 months.