The 36-year-old actor and Kelly, also 36, enjoyed a getaway to Cabo San Lucas, Mexico, over Labor Day weekend after sparking reconciliation rumors Aug. 31.
The From Dawn till Dusk: The Series star and Kelly first dated in 2012. Fans started to speculate the couple are back together after they went to Palms Thai Restaurant in Los Angeles last week.
"It looked like a date," an onlooker said of the outing to E! News. "They looked casual and relaxed. Yes, Wilmer was a gentleman and picked up the tab to pay for their food."
Sources told Us Weekly at the time that Valderrama and Kelly have been seeing each other again for about a month. The actor split from singer Demi Lovato in June after six years of dating.
"You have to be capable of being honest with yourself before you can get honest with other people," Lovato wrote in a cryptic tweet after word of Valderrama and Kelly's reunion broke.
Valderrama is known for playing Fez on That '70s Show and presently portrays Carlos Madrigal on From Dusk till Dawn. Kelly most recently appeared on the Hulu series The Path.