"He's really hot. That's why I didn't bring him," the Modern Family star joked to E!'s Giuliana Rancic. "He looks too hot, too tall, he takes a lot of space, and I was like, 'So listen, Joe, don't come.' "
Even without the eye candy on her arm, Vergara, 42, looked sultry as ever in a white Roberto Cavalli gown and Lorraine Schwartz jewels.
She and Manganiello, 37, have been heating things up since July, but the four-time nominee demurred when asked about what attracts her to the True Blood actor.
"We're having a lot of fun," she said. "We've been going out just for like two months and a half, and he's a really funny guy, which is something very important for me, and a very nice guy."
Vergara's costars have given their stamp of approval to the couple while affectionately chiding them for merging their over-the-top good looks: Julie Bowen said the two are "like a genetic explosion," and Sarah Hyland told PEOPLE, "They'll have really hot babies."