An eyewitness told ET the two arrived at the restaurant together in Valderrama's Tesla just after 8 p.m., and looked like "much more than just friends."
"They looked happy and relaxed in each other's company, and it seemed to be an intimate, romantic night," the eyewitness said.
"Wilmer was touching Minka's back as they were waiting to be seated," according to the eyewitness, adding that the dinner lasted an hour and half before the they headed back to Kelly's house. "They looked like a couple."
A source also spotted Valderrama and Kelly at a screening for his ex-girlfriend Mandy Moore's show, This Is Us, in Los Angeles on July 25. While the source didn't see any PDA during the screening, the two arrived and left together.
Valderrama and Kelly were last linked four years ago, while the 36-year-old actor and Demi Lovato were reportedly on a break, although he and Kelly never confirmed their relationship.
"After almost 6 loving and wonderful years together, we have decided to end our relationship," the two said in a joint statement. "This was an incredibly difficult decision for both of us, but we have realized more than anything that we are better as best friends."
"We will always be supportive of one another," they added. "Thank you to everyone who has offered us kindness and support over the years."