The two have been spotted on many PDA-filled outings over the last couple of weeks.
Over the last couple of weeks, fans have seen the twosome on multiple PDA-filled outings and it looks like they can't get enough of each other. An eyewitness tells ET that Mendes and Cabello enjoyed brunch at Dottie's True Blue Cafe in San Francisco on Friday.
"I feel like they are for sure dating," says the eyewitness. "I saw them kiss." In a video, shared by Pop Crave, the "Havana" singer and the Canadian crooner are seen getting cozy and locking lips in a steamy make-out session.
In the clip, Mendes is sitting next to Cabello and then puts his arm around her neck. The "If I Can't Have You" singer begins to stroke her hair before leaning in for the smooch.
A source tells ET that the rumored couple noshed on omelettes and pancakes, and that Mendes picked up the tab.
A second eyewitness also tells ET that they spotted the two at the Golden Gate Bridge that same day. "They were hugging and he was resting his head on hers [while waiting for a car]," says the second eyewitness, who also shared that a couple of fans approached Mendes and Cabello to say hi and they were very kind and said hi back.
Romance rumors first began after Cabello's recent breakup from Matthew Hussey, whom she dated for more than a year. The two singers then collaborated on a new single -- and sexy video -- "Señorita," and have since been photographed holding hands and spending time together.
However, a source told ET earlier this month that the two are "casually spending time together." "The two have always been close friends, worked on music together and admire one another. Camila just got out of a relationship and Shawn is on tour [so] the duo isn't looking to get into anything serious right now," the source said.
Cabello, though, opened up about her and Mendes' special connection in a new interview released this week.
"I’ve never had a lot of friends. I’ve always just had a few people in my life that I trust," Cabello told Clash. "I feel like it’s so rare to meet someone in this industry and find a person of that quality, and I feel like Shawn is that person for me."
"I just trust him, and no matter the level of intensity that he has around his career or I have, he is just normal, and that is so rare and precious to find in this industry," she continued. "To be able to hang out with someone and you don’t really care that they’re Shawn Mendes, you know what I mean? You’re just people, and that is definitely something that is rare."
Explaining that she's known him "the longest out of anybody in the music industry," Cabello said that "it’s been really beautiful to kinda grow up together."
"It’s actually a really beautiful feeling to know that this person is always going to be in my life, we’re always going to love each other," she added.
See more on the pair in the video below.