The 48-year-old singer thanked Shelton for "sharing [his] world" with her following an outing with 4-year-old Apollo at Lake Texoma, Okla.
Stefani posted several photos on Instagram and Instagram Stories from her day with Shelton. She wore a minimal makeup look, fringe crop top and beaded necklaces.
"#oklahoma #summer @blakeshelton thank u for sharing your world," the star captioned one picture, adding a heart emoji. "#nextstopvegas."
Shelton can be seen driving a boat in another snapshot on Stefani's account.
"Ok #laketexoma 2018 gx," she wrote.
Stefani also documented Apollo investigating bird nests on the shores of the lake. The singer is parent to Apollo, 9-year-old son Zuma and 12-year-old son Kingston with ex-husband Gavin Rossdale.
Stefani and Shelton visited Lake Texoma one day after Shelton's 42nd birthday. Stefani marked the occasion in a post to Shelton on Instagram, and followed up with a photo of herself with the country star.
"Birthday love u @blakeshelton gx," the singer said.