The 54-year-old actor wore a vintage shirt with his own face on it to the 28-year-old actress' Labor Day bash.
"We refuse to let #summer or #the80s be over! @nina @chordover #laborday," he captioned a photo on Instagram with Dobrev and actor Chord Overstreet.
The picture shows Stamos wearing 80s staples -- including neon short-shorts, a fishnet top and a fanny pack. His t-shirt features a picture of his younger self with the words "John Stamos."
Dobrev also posted a series of photos with Stamos on her own account. The pair spent the weekend on a lake with Overstreet, actors Lamorne Morris and Glen Powell, and other celebrity pals.
"Wanna know how we say hello to someone in the sacred language of 'Lake'? By throwing someone IN the lake. Welcome John. So happy you could join us. #LaborDayLakeLife #80sNeon #LetsGetPhysical," the actress wrote.
Stamos came to fame as Blackie Parrish on General Hospital and Jesse Katsopolis on Full House in the 1980s. He has since starred on E.R., Grandfathered and Scream Queens, and reprised Uncle Jesse on Fuller House.
Fuller House will return for a third season Sept. 22 on Netflix. The series co-stars Stamos' fellow Full House stars Candace Cameron Bure, Jodie Sweetin, Andrea Barber, Lori Loughlin, Dave Coulier and Bob Saget.