The 24-year-old pop star and 39-year-old singer-songwriter were spotted getting close at Catch L.A. restaurant Saturday in West Hollywood, according to Us Weekly.
Sources told the magazine Lovato and Mayer arrived at and left the establishment separately but appeared to hit it off inside. The pair reportedly "chatted it up for over an hour."
"John had his arm around Demi and was whispering sweet nothings into her ear. She was into it. They weren't making out or anything, but she was giggling the whole time," an insider said.
Lovato and Meyer collaborated on music in 2009 after Meyer complimented Lovato's song "La La Land" on Twitter. The pop star couldn't help but gush about the "Your Body is a Wonderland" singer in a subsequent interview with MTV News.
"John Mayer's been a huge influence on me. His songwriting really inspires me," she said. I guess he had heard I was a huge fan, and he sent me a letter. Then we ended up writing together ... It was like a dream come true."
The sighting comes nearly five months after Lovato's split from actor Wilmer Valderrama. The couple broke up in June after six years of dating, and Lovato told Elvis Duran and the Morning Show the next month that she's feeling "free."
"I feel really amazing," she said at the time. "I feel really great and I'm growing. My life is just really, really exciting for me because I'm growing. It's new and fresh, and I feel free."