The 25-year-old singer and 38-year-old actor appeared "super friendly" as they enjoyed a meal together Saturday, according to TMZ.
Lovato and Valderrama were spotted at Sol Y Luna restaurant in Tarzana, Calif. Sources said the pair were all smiles as they snacked on fresh guacamole at their table.
Lovato and Valderrama split in June 2016 after nearly six years of dating. The pair have documented friendly reunions on social media since, including at a barbecue at Lovato's house in June.
"Best of friends no matter what @wilmervalderrama," the singer said at the time.
In addition, Lovato discussed her lingering feelings for Valderrama in her YouTube documentary, Demi Lovato: Simply Complicated, which debuted in October.
"I've never loved anybody like I loved Wilmer, and like, I still love Wilmer," the star said. "We connected on a level that I've never connected with anybody before. He was just my rock, my everything."
"I think my heart's always with Wilmer," she added. "I think it was with Wilmer, it is with Wilmer and I think it will be with Wilmer, because you don't share six years with somebody and not give them a piece of their heart.