"boom here we go! It’s on @blakeshelton @kellyclarkson @johnlegend! @nbcthevoice premieres September 23 gx #lovethisshow #teamgwen #thevoice," she captioned the promo, which shows the 49-year-old bonding with Clarkson and her fellow stars.
"I'm very excited to see America's favorite couple fight it out," Legend says at one point. Later, Stefani asks her boyfriend, "You wanna fight, Blakey?"
At a contentious moment, in which Stefani blocks her boyfriend and busts out some dance moves, Shelton exclaims, "Why are you doing this to me? I thought you loved me."
In May, soon after fans learned that Adam Levine had decided to leave the show after 16 seasons, it was announced that Stefani would be returning to the show. While on CBS's The Talk in June, she said that being on the show without Levine will be "bittersweet."
"Adam was actually the first person to reach out to me when they were trying to pitch me the show," said Stefani, who previously worked on seasons seven, nine and 12 of the series. "He texted me out of nowhere, and I didn't even really know him [back then]. And he was like, 'You got to do it. It's the greatest show. It's so fun!'"
"It's going to be fun and exciting," she also shared. "Blake's my best friend. So, I get to hang out with him at work. It's going to be great."
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How Blake Shelton Got so Close With Gwen Stefani's Sons (Exclusive)
Earlier this month, a source told ET that "Gwen seems secure and happy to be back. Their relationship is so different from when they first started dating on The Voice. They're truly like a married couple who hasn't lost that spark."
The source added that for Stefani and Shelton, it "has been really sweet, because The Voice is where they fell in love, so being back on set seems to have stirred up some cute memories."
The pair first ignited relationship rumors in the fall of 2015, when they were both on the show. Just months later, Shelton's rep confirmed to ET that they were an item. They've been together ever since, however, they aren't rushing down the aisle anytime soon.
"They have talked a lot about marriage, but have decided that life has been so great that they don't want to rock the boat yet," the source also shared. "They are so incredibly in love and have supported each other through tough times. They truly are best friends and have made their lives work together despite their very busy schedules."
See more news on Shelton and Stefani below.
The Voice premieres on Sept. 23 at 8 p.m. ET on NBC.