Levine appeared on Howard Stern's SiriusXM show on Wednesday, when the Maroon 5 frontman said he never saw the relationship coming.
"If you had told me Gwen Stefani was going to be with Blake Shelton, I would have told you were out of your f**king mind," Levine remarked to Stern. "But it's so wrong, that it's right."
"It's super crazy, you think to yourself -- you're sitting in these chairs, and you're like, 'They're having sex with each other,'" he joked. "It's weird. It's like a dynamic shift, because you're just, like, it's wild."
When Stern mused that the timing of Stefani and Shelton's relationship may be wrong due to the two recently going through divorces -- 47-year-old Stefani from Bush frontman Gavin Rossdale and 40-year-old Shelton from country star Miranda Lambert -- Levine disagreed.
"I don't think you can really control those types of matters of the heart," he explained. "I think they found each other at a really interesting time in their lives. I see it as a beautiful thing. Good for them. And I think that love is a good, wonderful thing."
ET spoke with Stefani on Saturday
at the Kids' Choice Awards, when she admitted she was nervous to put her relationship with Shelton on the Voice
"I was like, 'This is going to be weird!' But, you know, the show is so real," she said. "All it is is us just being there and being us. So, it's been really fun."
"Obviously, any time I can be around Blake is a blessing," she added.