Shelton, decked out in a classy black-and-white suit and vest combo, started off singing by himself onstage before Stefani stepped out from the wings in a figure-hugging, semi-sheer gown covered in sparkly flower-print embroidery.
As the two performed their ballad, the couple gazed into each other's eyes as they sang and it was clear how well the duet worked for the two of them and how much emotion went into their live performance.
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As the heartfelt duet came to a close, the audience and Shelton's fellow coaches rose to their feet for standing ovation, while the cute couple embraced on stage and smiled as the lights dimmed. Shelton even bowed down to his lady love as the audience cheered.
The performance was recorded an hour before the live show kicked off at 5 p.m., and the two stars ran through the entire number twice to get the best take.
ET was on the scene at The Voice, where audience members at the taping were treated to a little more than viewers at home -- including some gentle ribbing by Shelton's fellow coaches.
As Shelton and Stefani took the stage, Pharrell Williams playfully joked, "Aww, you guys look so cute!"
Even The Voice hype man, who is responsible to getting the audience pumped up before the show, teased the country crooner's sophisticated style, telling Shelton, "Look how good you look tonight! Gwen dressed you awesome."
Shelton spoke to ET's Sophie Schillaci before taking the stage on Monday, where he admitted that he dressed up to impress his rock star girlfriend. In fact, he said the track itself was an effort to win her over.
"When I originally started writing this song that we're performing tonight, I was only trying to impress Gwen that time around too," Shelton revealed.
He added that the song "was just kind of something for she and I to help us feel better about what we were going through," referring to both of their divorces.
The morning before the big duet debut, Stefani shared a super sweet Instagram pic of the adorable duo in a romantic moment in the woods.
Shelton previously opened up about the song back in April, telling ET, "[The song] is very personal for us both because, you know, we obviously have this bond that is remarkable together… I hesitate to brag on it too much but I really think that it's as good of a song as I've ever written in my life."