Gigi, 24, dressed down for the occasion in jeans and a white top. Tyler, 26, also opted for a casual vibe in shorts and Vans sneakers.
Serena, 37, rolled solo without husband Alexis Ohanian.
The supermodel and the tennis star are longtime friends. Serena gushed over the Vogue cover girl while presenting her with the Glamour Woman of the Year award in 2017.
"Gigi, you are one of the few people on this planet I would leave my baby for — for one night — but for you, it shows how much you mean to me. And I want you to imagine the effect you have on the world," Serena said at the time.
She continued, "Since I’ve known Gigi Hadid since she was a kid, she’s always been a woman with goals. Not only beautiful on the outside but totally stunning most importantly on the inside."
Gigi introducing The Bachelorette star to her close pals is a big indication that they're moving towards being an official couple.
The catwalker is "really into" the reality star, a source told Us Weekly.