A source tells ET that the couple is 'truly like a married couple who hasn't lost that spark.'
A source tells ET that "Gwen and Blake have been having the best time while shooting The Voice. They laugh so much on set and backstage, and aren’t shy about showing their affection and are better than ever."
"Gwen seems secure and happy to be back. Their relationship is so different from when they first started dating on The Voice," the source explains. "They're truly like a married couple who hasn't lost that spark."
The source also adds 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."
Stefani's return to the singing competition show comes after Adam Levine announced his departure from the show after 16 seasons, explaining that it was “time to move on,” in a lengthy Instagram post on May 24.
"It’s going to be fun and exciting," the "Hollaback Girl" singer, who previously worked on seasons seven, nine and 12 of the series, said during an appearance on The Talk. "Blake’s my best friend. So, I get to hang out with him at work. It’s going to be great."
ET also sat down with Shelton in June, where he admitted that it was "hard" for him to see Levine leave.
"I can't imagine, honestly, what the show is gonna feel like at first without Adam there," he confessed. "I mean, we're about to start filming the 17th season of the show, and Adam has been my frenemy from day one, you know, down there on the end."
He also touched on how happy he was to have his girlfriend back on set. See more in the video below.
Reporting by Adriane Schwartz.
Gwen Stefani Says It’s ‘Bittersweet’ to Rejoin ‘Best Friend’ Blake Shelton on ‘The Voice’ Without Adam Levine