Casalegno and Thompson debuted their first picture together on Instagram, shared with a playful caption. "I like California 💕😜," wrote the "The Summer I Turned Pretty" actor, while Thompson shared, "I like Texas 😜💕," each mentioning their other half's home place.
In a 2018 YouTube vlog with Krissy Jane, the model opened up about how the couple started dating. "We actually met off of Instagram," Thompson said. "We chat with a mutual photographer, and the next week Gavin and I are shooting with her, and she's like, 'Oh, my God, you have to meet this person. You guys would be so cute together.' So, I went onto her photos and saw a picture of Gavin, so I liked it, he saw my like and came onto my Instagram, and he slid into my DMs."
Casalegno continued, "And then I asked if she wanted coffee, 'cause I'm a huge coffee lover, like, 'Do you want to go get coffee sometime?' And she was like, 'I don't coffee.' You know, I was like, 'That's gonna be a struggle.'" "That's strike one!" Thompson joked. In an April 2021 post, Thompson confessed that her beau has finally turned her into a "coffee drinker."