The young pop stars were spotted packing on the PDA in Miami, Florida, on Monday, and now, a source tells ET that the two are "committed to working on a relationship."
"Shawn and Camila originally were just enjoying spending time together and having a summer fling," says the source. "Camila had just got out of a relationship and Shawn was in the middle of a massive tour."
"However, Shawn and Camila have really fallen for one another," the source adds, noting that the former Fifth Harmony star has been traveling with Mendes throughout his tour.
Reps for the singers did not reply to requests for comment.
Cabello was most recently spotted supporting Mendes at his show at the American Airlines Arena in Miami over the weekend. In a video posted by a fan on Instagram, the "Havana" singer can be seen sporting a white dress while dancing and clapping along to her beau's music.
Cabello, 22, and Mendes, 20, have been spending plenty of time together in recent weeks, after releasing their spicy collaborative hit, "Señorita."
Hear all the details on their PDA-filled outings in cities like Malibu, San Francisco, Tampa and more in the video below.