The 48-year-old singer and 42-year-old country star spent Saturday at Lake Texoma in Oklahoma with Stefani's three sons, 12-year-old Kingston, 9-year-old Zuma and 4-year-old Apollo, according to KFOR.
Stefani shared a number of photos and videos from the day on Instagram Stories, including a picture of Shelton nuzzling her neck.
Stefani wore a printed top with several beaded necklaces and a baseball cap.
The "Used to Love You" singer also posted a snapshot of Shelton with her son Zuma.
"Double cute," she captioned the photo.
Stefani is parent to Kingston, Zuma and Apollo with her ex-husband, Bush frontman Gavin Rossdale.
Shelton said in an interview with "Today" in March that he loves being surrounded by Stefani's children.
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"I never saw that coming. But it's so fun," the star said.
"At this point in my life, I kind of had put [having kids] as like, 'Well, that wasn't meant to be.' 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.
Stefani kicked off her Las Vegas residency at Zappos Theater at Planet Hollywood in June with Shelton in attendance.
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