The 23-year-old singer posted a photo of herself and Gomez making funny faces for the camera, writing, "Look at how #coolforthesummer we are.. Friends for years, #sameoldlove."
The picture marks the first time the stars have been photographed together since the unite4:good gala and unite4:humanity event in February 2014. Gomez appeared to initiate the reunion by wishing Lovato a happy birthday Aug. 20 on Twitter.
Lovato and Gomez both starred on Barney & Friends in the early 2000s, and went on to pursue Disney Channel careers. The women admitted their friendship had cooled in 2014, with Lovato telling Watch What Happens Live, "people change and people grow apart."
"I've known her since we were 7, and we did fall apart for a while," Gomez explained to Seventeen earlier that year. "She was going through things and I was so young and it was confusing ... I don't think [my reaction] was fair, and I'm so happy that I have her back in my life now."
Lovato will release her fifth studio album, Confident, on Oct. 16, and bring her Demi world tour to a close in Madrid, Spain, the same day. Gomez debuted new single "Same Old Love" this week, and is scheduled for an adaptation of The Big Short with Brad Pitt.