The 40-year-old country star was spotted with Stefani and her three children, 10-year-old Kingston, 8-year-old Zuma and 2-year-old Apollo, in Lake Arrowhead, Calif., TMZ reported Sunday.
Shelton, Stefani and her sons took a road trip to the popular vacation destination, and were seen strolling and dining out, according to E! News. Lake Arrowhead is located in the San Bernadino Mountains, about two hours outside Los Angeles.
Shelton and Stefani confirmed their relationship in November 2015 after splitting from their respective spouses, Miranda Lambert and Gavin Rossdale, earlier that year. The country star couldn't help but gush about Stefani on The Ellen DeGeneres Show this month.
"I love talking about Gwen," he told DeGeneres. "It's been just an eye-opener to be with somebody like her."
"Believe it or not, you think Gwen Stefani and No Doubt, and she's literally maybe the most normal person I have ever met in my life," the singer said. "It's been good for me to be with somebody that's so grounded and a good human being with a great heart."
Shelton previously enjoyed family time with Stefani and her sons at his Tishomingo, Okla., ranch over Labor Day weekend. Sources told Us Weekly in June that Shelton, who has no kids of his own, is thrilled to be bonding with Stefani's sons.
"[They've become] closer and closer," an insider said. "The boys love him ... Blake always wanted a family, and it's looking like he got one."
Shelton last released the album If I'm Honest in May, while Stefani released This is What the Truth Feels Like in March. The couple will both serve as coaches on The Voice Season 12.