The 41-year-old country star couldn't help but gush about Stefani in an Instagram post Saturday following the 48-year-old singer's latest visit to his ranch in Oklahoma.
Shelton shared a photo of a collection of arrowheads that Stefani has found on his property. He said in the caption that the "Make Me Like You" singer has a knack for finding the artifacts.
"Hey @gwenstefani it's official... with your arrowhead finding eye you are now an adopted Okie!!! Side note: I love you pretty girl... #truth," Shelton wrote.
Shelton and Stefani often visit Shelton's ranch in Tishomingo. Stefani, who shares 11-year-old Kingston, 9-year-old Zuma and 4-year-old Apollo with ex-husband Gavin Rossdale, spent spring break with her sons at the property in March.
Shelton said in an interview with Today the same month that having Stefani's boys in his life is a "fun" and meaningful experience.
"I never saw that coming, but it's so fun," the country star said.
"At this point in my life, I kind of had put that, like, 'Well, I guess that wasn't meant to be' -- and then all of a sudden it happens one way or another and it's like wow, I really missed out on a lot," he added. "So having them around is, I don't even know how to describe it, it's so much fun."
Shelton and Stefani confirmed their relationship in November 2015 following their respective splits from Miranda Lambert and Rossdale.