Meanwhile, Colletti kept things fresh in a white shirt. He appeared to be wearing a watch on his wrist that was tucked around Cavallari's waist.
The post received more than 125,000 likes in just 30 minutes and her followers haven't been able to control their reactions to the snap.
"Oh my God," wrote one Instagram user.
"Go ahead, Kristin Cavallari, break the damn internet," another quipped, adding five clapping hands emoji to their comment.
"OMG no f-ing way," added a third. Several others echoed that sentiment, wondering if the former flames are actually back together. The cozy picture could simply be showing two long-time friends just catching up, but Laguna Beach fans are seemingly hoping for more.
This is the first time Cavallari has posted a photo with a guy since her split from soon-to-be ex-husband, Jay Cutler. The two announced their decision to divorce in a joint statement back in April.
"With great sadness, after 10 years together we have come to a loving conclusion to get a divorce. We have nothing but love and respect for one another and are deeply grateful for the years shared, memories made, and the children we are so proud of. This is just the situation of two people growing apart. We ask everyone to respect our privacy as we navigate this difficult time within our family," the former couple said.
No word on whether or not the two reality stars are dating or if they're just friends, but fans will certainly have their eyes glued to social media in hopes of finding out what's really going on between the two.